Since you're talking b&m, I'll take a shot at this. I only play live and I only play limit.
1. If you're very good 2/hr is certainly possible at the lowest limits. I know nothing about your skills so I can't say anything about your expectation, of course, but the important part is that it's possible.
However, it's not a smart thing to waste time at 2/4 if you're any good. For people who know they are good players it makes more sense to scrape up a larger starting bankroll and start at like 4/8 or 6/12. Those games in most rooms either play the same or pretty close to 2/4 and the rake isn't nearly as brutal.
I would be inclined to tell you to stay at 2/4 until you have a good idea of what you're doing. Most players transitioning from NL to limit have a really tough time at first. They really are completely different games. Going limit to NL is much easier for most people.
2. The short answer is that every casino is different. It would really help if I knew what room we are talking about. It's unlikely that I don't have at least a passing familiarity with yours. At my hometown room, Canterbury Park, all the games on the weekend are good but you do have to exercise a little game selection during the week, especially during the day. A good game can always be found at limit below 15/30, though.
3. Absolutely not. You'll see improvement in the play starting at about 4/8, 5/10 or 6/12 but the play doesn't improve that much. In some rooms the games get tougher at 6/12 or 8/16. SSHE is applicable at every level of the game to varying degrees. It will be directly relevant up until about 15/30 in the current environment.
4. No. There might be some disagreement about this, but I think the limit section of either Super System book is useless. The Baldwin section is the original is outdated and the Harman section in the new one offers very little advice directly relevant to small stakes games. Get yourself a copy of
SSHE.
If you're going to be serious about taking up limit I would like to be the first to welcome you to forum and I look forward to seeing some of your hands.