First, the easy part: 'as much..' is for nouns, eg: as much money. 'in love' or 'at peace' are not nouns, they are states.. so 'as much' doesn't work in these sentences. Now, the difficult part: 'as.. as..' is simply for comparison, so 'I've never been as in love as he is' would be correct, however, 'so..' shows a new high extent, so 'I've never been so in love (as I am now)' is also correct, but the nuance/focus is different.

'I have never been so at peace with myself as I am now' is correct

I have never been so at peace with myself as I am now. I have never been so in love as I am now.

Gabriel, Dude! the Word "Much" takes literally always the word "as" and they shaped the expression "as much" but the other Expression is "so in love" means love it so much but not saying "as much as in love... etc" it awkward that's it you don't have to disturb your self comparing