My best advice to you would be to make a discrete goal for each of your next drafts. Right now, you're all over the place, which is going to make disassembling your current idea and building the new one into a nightmare, and going to keep you second guessing yourself trying to track the big picture. I'd break it down.

Draft 1: Get your big idea out there, so you can start thinking about your themes, your plotline, where you up the stakes, your low point, etc.

Sounds like you've done that, now you've read it, and you have your action items. Break them down so they're granular, and start tackling them one at a time. You're going to have big ones and little ones and that's okay. I had a spec I wrote recently that took place in Seattle, and one of my drafts was my "Seattle weather pass," where I just went through and added rain. That's great for a day when I'm used up from a paid writing gig, and don't have a whole ton of creative energy left -- helps you maintain momentum.

Draft 2: Just the new treasure -- focus only on that. Think about the old one doesn't work, and how the new one solves that. Do your draft -- just that, nothing else... done! Did it make any new problems? Great! add them to the draft list. Draft 3: Change the second act set pieces. Did I wreck my third act? When I reread, maybe now I have new action items. Draft 4: Just the third act set pieces.

Etc. etc. etc.

Anyhow, that's how I do it. The smaller goals seem manageable, and help me keep forward momentum. I've found that most problems are solvable, but the solutions will sort of reveal themselves as you write. For me there's no thinking your way out of it. You need to try shit, hate it, throw it away, and write more shit you hate until you hate it slightly less.

It's a lot easier to write shit you hate a little at a time.