Hey, man, welcome home!
The 4-Gig patch, AKA the 'Large-Address-Aware', lets your PC use more than the usual 2 Gigs of memory when operating SH3. It's not necessary for the stock game or GWX, but is absolutely vital for large mods like the Merchant Fleet Mod.
1. H.sie's patch corrects a lot of flaws in the game, like not having the WO come to the bridge when you surface, making the WE's range estimations a little less precise (it rounds to whole numbers), and fixing a bunch of minor headaches. It's a good one.
Here are Blitzkrieg's code-names for all mods:
http://www.subsim.com/radioroom/show...3&postcount=15
2. I don't use widescreen, so someone else will have to answer that.
3. Yes! Answered in (1).
4. More fun? Debatable. As fun? Yes. The Wolves of Steel supermod makes it fully playable, and a lot of people play it and love it. It still only has the four variations of the Type VII and just a handful of merchant types, but there are people trying to fix that. It looks great, but I can't live without my Type II, so I still stick with SH3.