1) Don't think so. But keep in mind, that raising GDP works the long way by boosting your countries economy while your naval budget works the short way. Always choosing Naval budget at the cost of lower GDP is not the best choice you can make.
2) When the difference between VP is to high, enemy tends to ask for Peace. I never had a problem getting the enemy to want a peace
3) VP seem to be connected to "estimated battle performance" or something like this. The more tonnage and armament a ship has, the higher the VP also age and technology levels seem to be important.
4) 2 isues here: 1. Sometimes if Ships are showing only minor damage that does not affect combat readiness, AI does not send them to port automatically. 2. Enemy has a chance to catch up damaged ships on a following battle while they are on their way to the port.
5) Can' say anything about it. My enemy has to rebuild ships and not repair them after an engagement.
6) I seldomly play auto battles because of the sometimes iffy results.
7) No. Or better not yet. Don't think it will stay this way.
8 ) Enemy asks for peace as mentioned before
9) Never tested it.
10) Had similar issues when I started playing. Had not enough crew training, so my crew were recruits or greens. They miss alot. With regular or higher crew levels my ships esp. the BBs shred enemy rushing TBs or DDs. Maybe there is also an issue with your ship designs. There are several factors ingame that have an effect on your aiming. Like weather, daytime, stability of your ship, etc. Also ammo choices and barrel length affect aiming and your ability to seriously hurt those DDs.
Then there is strategy. keep enemy DDs at arms length (out of torp range) by changing course fast enough.