I am going to take this one question at a time so I can give the best answer:
"What is the purpose of the mitzvot? "
The purpose of the Mosaic Law and the commandments ("Mitzvot") as far as I understand, is to keep your soul pure and right with the will of the Creator. It's a matter of physical well being and what we call "spiritual" well being, and this brings up the question of what exactly is "Spiritual" well being. The Dietary Laws for example, I believe are for the benefit of both the bodily health as well as the Soul and one's relation to G-d. What G-d wants is for His people who are separated unto His own "Church" or "Assembly", as I understand, to be as "Holy" as possible. The meaning of "Holy" another difficult concept to describe, but the idea is to be "godly" or "close to as perfect as possible", or "That which is considered noble and angelic". The opposite would thus be "unholy", and all things which are "unholy" are loathsome to Him, so therefore, He desires for His people to be as "Holy" as possible and not do anything which may stain their honor and spiritually purity so that they descend from this state of Holiness. To be pure from dishonor and stain from sin, one must engage in some sort of "Sacrifice", and the Torah is very much about how to properly conduct this most holy of processes, which can possibly be defined as a "ritual".
One of the most oft-questioned issues of Jewish Law, especially in regards to the Moshiach, is how the whole Torah can apply if the Sacrifices aren't being followed, often using the Epistle to the Hebrews' as rationale. While I agree that there was a concept of the Malchezdiek priesthood (David mentions this concept in Psalms, about the Moshiach being a "Priest forever in the order of Malchezdiek), I think the Epistle to the Hebrews perhaps had it wrong: There will one day be a resurgence of the Temple sacrifices.
The Sacrifices, which are impossible without a functioning Temple and Priesthood (and perhaps I will get into the issue of the Epistle of Hebrew's canonicity later), were to serve as a sort of "payment" for one's offenses, similar to how one would perhaps offer a gift to one whom they offended or some kind of restitution. In addition to such, they also served (and will serve again according to my interpretation of what will happen in the age of the Third Temple and Christ's return on Earth, which I will perhaps cover on the "Who is Jesus" question) as a means of showing Thanks for the blessings that the Israelites were bestowed with such as bountiful harvests and flocks, and victory in battle and healthy offspring and being saved from dangerous situations, safe travels, anything anyone can imagine which would be worthy of showing acknowledgment of being directly blessed, and even though they were commanded to offer such sacrifices, it can be seen as a sort of test. In a somewhat similar example, one would plant the very finest of their Corn in the ground to ensure that the next crop would be like the one planted. Such as, perhaps by sacrificing the finest of the firstborn of the flocks, the shepherd would be blessed with healthy livestock, the vineyard would be blessed with good grapes if the finest wine was sacrificed. Additionally, the sacrifices themselves served to give the Priests a means of existence since they were forbidden from private ownership of land, yet their function was to serve the Creator's will in the Tabernacle and Temple.
I will get into the issue of how issues like the Dietary laws are misconstrued and misapplied (and incorrectly dismissed) by the "Christian" movement perhaps in the next installment about who Jesus was.
Now there is an issue called "Abomination". Many translations, trying to dance around the actual meaning of the word, call it "Ceremonially unclean", as if that somehow does justice to the term. What does "Ceremonial" mean? What kind of "ceremony" is going on? The idea of an "abomination" means "Horror/Terrible thing/monstrosity/something you avoid at all costs". Someone blowing their nose in your coffee can be even seen as close to the term of "Abomination", would you simply call your coffee "Ceremonially unclean" after such? Of course not. Likewise, things like adultery and various sexual prohibitions which are called "Abominations" are not just "Ceremonially unclean" , they are considered absolute horrors which are worthy of the death penalty, which is another taboo subject in itself.
Another common concern is how the Death Penalty would apply to crimes in the Torah of which it's laid out. The answer is....it can only really be exacted by a completely autonomous Legal Council among Israelites, and (most likely) only in the Holy Land/borders of the Holy Land itself. Therefore, one is not justified in carrying out the actual penalty themselves for those guilty of various crimes like adultery or even breaking the Sabbath. There is much debate on this issue. I have broken the Sabbath many times in the past until I took it more seriously, perhaps I will die for it one day, perhaps I can repent of it, this I don't know, but I do believe that anything which carries the death penalty or permanent exile will be done through Providential Fate (i.e. by Heaven's decree and direct action) rather than through man's hands. It appears that there may be a certain "hierarchy" of sins, even among those that are death-penalty level. The Rabbis assert that the death penalty can only apply to those who are caught in the act by several others (a theme we also see with a variant in Islam in various regards), so one is only to be put to death if others catch them breaking the Sabbath, I don't know if I believe this. But I'm going to jump on the difficult "grenades" of what exactly the Mitzvot are: One who is guilty of a death-penalty crime has earned himself a death-sentence, perhaps a shorter life span, perhaps a painful fate of sorts. What exactly, I do not know, BUT I do believe that anything that is forbidden should be avoided altogether, and everything that is commanded should be followed, as possible (i.e. no trips to the Temple when there is no temple), and the ones that are possible even if they are considered an inconvenience (i.e. telling one's wife to sleep in another bed during her "cycle") are in fact necessary to be followed if one wants to be truly right with the Lord.
I do not believe Yashua in any way anulled any of the commandments, and I strongly suspect any verse which may indicate he did to be an interpolation. Some things can make this difficult, as it leaves much ambiguity: The story of the Adulteress woman, for example, is called the "Pericope Adulterae", it is almost universally regarded as a false addition, an interpolation that is generally considered an add on to get around the aspect of putting adulteresses to death (at least in the autonomous Israelite kingdom). Because this story is fake, one could argue that in the context of Jesus's time, (and perhaps again in the Third Temple age when he rules from Jerusalem) Adulterers/esses are very well to be stoned to death like how it's done in numerous countries today, but most certainly not in countries where this legal autonomy is not in place.
This is the end of part 1 of part 1, if you have any questions before finishing the issue of the Mitzvot and continuing to the issue of who the Moshiach is, I will address it as I can.
