1. Yup.. seems like your amp is overheating. Perhaps you don't have enough room to dissipate heat. Or maybe you got the gain turned up too high.
2. (a) DON'T SPEND YOUR MONEY ON A CAP YET!! Upgrade your battery, and ground cables that run to your alternator, and to the chassis. It should solve your problem right then and there. If you really are getting annoyed from dimming lights, you could try putting caps on your headlights, rather than your amp. (b) I had the same problem with it turning off. I'm planning on running direct power from the battery to see if it helps.
3. Most likely, you'll get more bass. A lot cleaner, and tighter as well. Just switch over.
4. Mount the mid in your door, and your tweeter in the a-pillar. The adapter would work well. You could make your own if you desired.
5. That'll do
6. They're decent subs. In my opinion, i'd sell them and go with a
beast AL 1804 or a
baby beast AV 15 I own both of them beasts.. i heard the AV 15.. and it blows away my older JL 18w6 18" sub. The specs, and the way the AL 1804 is built, will definitely blow the AV 15 into the dirt.... as soon as i get a chance to hook it up. A JBL 600.1 would work with the AV 15 perfectly.
Ren.