I think that when u get all your skill things (on the left of skills) you should be able to transfer them to the one which lets you upgrade con and dex etc. + if you agree
How to ace the last boss: get gun spawn hope for a sniper then quickly get to bottom level and stay directly underneath him till he jumps down the shoot 'im. BTW dodge his bullets as he flys down into the abbys :)
This game is really easy: just send 20 or so halbediers on 1 lane till they get to the end, then send infinite spears on the same lane. This should fill the bar up at least 3 quarters :)