I have never seen Psalm 110 as showing Jesus is God. However, clearly whomever David is referring to is the lord of David. The Psalm seems messianic to me and it seem to the Jews that Jesus was speaking to, and so the Messiah, the man who would come as the Messiah is said to be the lord of David.
Jesus was just asking how the Messiah could be lord of David and also the son of David.
I see no difference if Adonai is spelt with a capital or lower case L, the meaning is the same.
For Christians the Psalm is Messianic since Jesus said so (and it seems the Jews of Jesus day also saw it that way) and because Jesus did offer Himself up as a sacrifice for sin (as per Isa 53) and became the High Priest in the New Covenant, (doing away with the need for the Levitical priesthood) and because the Psalm, even if it originally may have been about David who acted as priest it seems at times, with the blessing of God (unlike Saul) and was King in Jerusalem, as the Messiah is also King of the Jews in Jerusalem. But on top of these things, it surely is the Messiah who is going judge the nations and rule over them (see Psalm 2)
First, I want to say that I respect your point of view eventhough I don't agree with it.
The important detail is that verse in Hebrew in psalm 110 says "adonee" which is better translated as "my master". However, the author of the book of Matthew changes that. Instead of using the greek word for "master" (
Strong's Greek: 1203. δεσπότης (despotés) -- lord, master) they use the word for the name of God (
Strong's Greek: 2962. κύριος (kurios) -- lord, master). See below:
Notice that in the greek, it's the name of God (captial L, Lord) listed twice. Take a look at the actual Hebrew of Psalm 110:
Do you see how the author of Matthew changed the verse? Things like this cast serious doubt on the accuracy of the NT. The short episode in question was intended to show how the pharisee was not able to answer the question. But the question is based on a mistranslated verse in Psalms.
This is why I said: "It's a flawed conclusion based on a flawed translation." The flawed conclusion is: "The pharisee couldn't answer the question." A more likely conclusion is: If this episode actually occured, the authors of the NT changed the story to make it look good for Jesus and make it look bad for the the pharisee. By changing the words of the psalm, the authors of NT showed they were willing to sacrifice accuracy in favor of making Jesus look good.
If the episode occured, I expect the pharisee would have answered either that the psalm was being misquoted, or they would have answered that the Jewish Messiah is a King. A King is the master of the entire kingdom including David. The father-son relationship wouldn't change that. This is obvious if the psalm is quoted correctly using the words "
my master"
, not "lord".