What? If a Thiest believes God is the most important thing in his/her life and seeking God's pleasure is his/her objective and still the Thiest sins then something in the former part of this sentence suffers from lack of certainty. The very fact that a Thiest claiming 100% certainty in accountability simulataneously give a higher priority to some other feeling shows the lack of substance in the claim.
No, it doesn't. People have different priorities at different times. For one, maybe seeking God's pleasure includes doing certain things that you consider "sins". For another, a lot of people who believe in God don't feel that God wants them to constantly seek his pleasure. Many theists feel that God just wants them to live their lives and be happy. People who do believe in eternal punishment for sins only commit those sins due to extenuating circumstances. Most people who commit sins that would cause them to be eternally punished according to your standards don't believe they will be punished because their actions aren't "sins".
And that has nothing to do with the topic. Forget about the differences. All I am saying is that if A believes 100% that he/she will be held accountable for a sin and still A commits that sin means A is not 100% certain and it is wrong of A or anyone else to think that he/she is 100% certain. By bringing in the differences in religions you are not furthering your argument.
This is why we've gone over this already. The point is that you think certain things are sins and will cause people to be punished eternally, and assume that everyone who believes in God must feel the same way about those actions. I'm trying to tell you that's not the case. The one possibility to prove this argument wrong is that people who commit the sins you think will cause them eternal damnation don't see them as sins at all. The other possibility is that, even if they see them that way, whatever the sin is, is more important than anything else when they commit it.
If saving yourself from Hell is not your top priority and earning God's pleasure is not your top priority at any time and SIMULTANEOUSLY you claim that earning God's pleasure is your top priority then your certainty in the latter is not there.
To be 100% certain that a camera is watching you and to be 100% certain that the camera knows all your actions and still you steal, cheat, lie, etc. ... these two can not happen together.
The problem is that this is a complete strawman. People who kill either have a good reason, like saving their own or someone else's life, or they forget about the punishment due to anger or other strong feelings, or they don't think they'll be punished for it, or they think they deserve punishment and crave it. (There are many other, more detailed reasons, but these are the major ones)
Some people do know there are cameras watching them while they steal, cheat, lie, etc. and yet they do it anyway. I'm not sure how many times I have to say this, but people do this for many reasons.
The bottom line is that people make mistakes. People forget things. People look at things differently.
Some people don't believe in God, so they are just ruled out.
Some people believe in a God that doesn't punish people in Hell at all, so they are ruled out.
Some people believe in a God that punishes people for some things, but has a different list of those things than your God does. So, they are sure of God and His punishment, just not for the things they are doing (even though you believe they will be punished for those things). This rules them out of your OP, too.
Some people believe in your God and His punishment for all the same things you believe he punishes, but they commit these sins because of extenuating circumstances. They commit them because their rage or jealousy or love or just general short-sightedness overrides their knowledge of future punishment. This is the group you're referring to, but this is why they commit those sins, not because they're not sure about God's or Hell's existence.