well just a few thoughts on your post: I've been a 'believer' for decades but I don't consider myself a 'true Christian' either.
You say you have battles in your mind between sexual desire and purity: do you mean that there is already a battle going on or that you think there might be in the future?
What do you mean by the 'golden rule'? What is the 'law in its entirety' the way that you see it?
And I think you hit the nail on the head with your bit about 'the gap between the perfect and the imperfect'. The person who is really holy knows that there IS no gap! He is the one who sees all the faults of mankind in his own being and cannot bring himself to judge anyone else without feeling, as you say, sickened because he knows, in his heart of hearts, that to do so is merely to condemn himself . . . that is someone who is much closer to God than he realises.
And then you say that God just wants us to get on with each other. Again you're absolutely right! Yes I think that's all He wants: and He wants us to care for those who cannot care for themselves and to be merciful with those who are weaker than we are . . . .it's just such a shame we don't seem to be able to do it very well :(
as to your bit about how our 'mistakes and inadequacy are constantly being revealed to us' making you feel ill: well, I'm not surprised about that, but that sounds a bit like panic to me: loads of time to worry about all that later. First thing: go back to the source: take it right back to the beginning and read the gospel (preferably one of them from end to end) then see what you think.