Here's my opinions on some of your questions:
1. I think so. If you are going to be throwing larger flies, or in windier conditions, the 6 is noticably less work than a 4. I don't usually have to cast overly far, so I use a 4 for the most part, but if I think I'll be into more bass than bluegills, I use the 6.

2. I don't know about the 9' Forecast 4 weights, but I really like the 7 1/2 and 8 footers. They are med/fast. I'd opt for the 7'6" or 8' option, even in a tube. Just learn to keep your backcast up. A longer rod isn't the only solution.

3. I think that is kind of backwards from my experience. Double foot guides mean double thread and finish, which puts more weight onto your rod and will reduce performance. Best performance is the lightest guides and wraps that you can come up with. Blank design these days has reached a point where the extra ferrules won't impact your rod action like it did in the past. More sections don't necessarily mean stiffer.

5. Not at all. I use single foot guides a lot, either with ceramic rings or single foot snakes. I usually try to put a locking wrap on them, though.

6. It isn't difficult at all.

7. Spine each section individually.

8. I usually wrap 2 times the diameter, or whatever the blank maker suggests, whatever is longer.

9. I think it is just as easy, just different.

11. Hand rotating is very effective, but more time consuming.

I'll send you an e-mail on some other things, too.