hispls 5,000+ posts
CarAudio.com Veteran
We used a bit of that building the wall in my Jeep. More hassle than its worth if you can think up a better option for joinery but my buddy from Poland always buys new tools when he visits and he was staying with me here when I did that build and just happened to buy one of those sets.I have a Kreg jig and plenty of proper pocket hole screws for 3/4 ply. Those are pretty damn sturdy joints.
Otherwise your wall of text is a bit intimidating particularly if you're fishing for comments/feedback/answers on 20 different things.
Perhaps start a new thread as a build log, start posting pics, explain your immediate plan and just take it one step at a time as you go. I do not believe that this type of project done right is happening in a single day.