Before starting my post, I will apologize for the late reply. I've been busy lately, and only came across this post on Sunday, and finally got time to answer your post.
With your first point, after realizing my stupidity with the 2nd and 3rd bosses stuff, I probably quitted trying, and that's why there's a huge gap with the 3:17 from November 23, 2009 and the 3:10 I posted in March 29, 2010. I can't remember why I have decided to give it a try again after so long (maybe I wanted to have a record for myself, I don't know).
With the second point, I also think the level could be done a few seconds faster, but I got no idea on how to do it. How perfect I think 3:10 is? I don't know, it's pretty hard to give a precise estimation on how perfect the stat is, since I haven't replayed Death Egg Act 2 like I did 3 years ago, with that much practice. I lost that in the 3+ years the stat went live.
With the third point, after looking at the map, I think I got my route back deep from my brain: Straight until the first tunnel, there's an electric shield at the start, which as you said, is quite required for the run I made. Then, I went in the tunnel, went RIGHT, then followed the path. Some extra notes: I quickly spindashed in the first set of staircases so I could squeeze in and gain some time (probably got that after watching mike89's run, which is in the video section), and I mostly followed mike89's run (of course, about the 1:16 mark, I did follow the normal route, as I can't fly as Sonic over the teleporter). From the first boss, I think I got lucky, because, as far as I can remember, I remember nothing about it.
And with the last point, as I said in my previous post, I'm pretty sure I was decided to get a record, and (I still can't remember for sure) decided to do Death Egg Zone Act 2. Maybe because it was the hardest one. Maybe because not many people have done it before. I don't know. What I do remember (and you are right about it) is that I played DEZ 2 over and over again, for some weeks, and that was probably the only one time I actually got that far into speedrunning. I haven't really focused as much as I did on DEZ 2 in other zones, and that's why some (if not most) of the stats aren't really considered speedrunning. Most of them I probably did for the heck of it, and I'd guess I made them as a filler, in order to gain a higher spot in the S3/S&K complete ranking list.
And, finally, as I said in my last post, I don't really much care about what happens with the 3:10 stat. I only wanted to clear it out that I did not lie by posting the 3:10 stat. It was all done legit, in an emulator running at full speed (because I don't own a Mega Drive), starting from the level select screen, selecting Death Egg Zone Act 2. I did not start with the lightning shield, I obtained it before the first tunnel. Anyway, I don't care about it as much as I did 3 years ago, and if it seems needed, it should be removed, and I will not complain. I don't have as much time as I had 3 years ago in order to attempt to speedrun DEZ 2 and try to get close, tie (or even beat) the 3:10 mark. And that's the reason I haven't been able to actually answer to your post. Hope this clears any doubts.