Help with swim part of BT oly training plan

I don't come from a swim background at all; I just started last fall and along with most I'm kinda learning as I go, just praying not to drown or get drug to the bottom by a state record catfish...

The beginner Olympic plans here on BT have short swim days, where it says you do speedwork. Everything is in mins., not yardage. Do I just do 50m repeats for 24 mins for example? It says "(5x100, then 10x50)" or something like that. A "speedy" 100 is prolly a stretch right now, I've been working so much on form and going ~2:00 per, I'd drown if tried to fly through one.

Right now I can do 50's in the low 40's without pushing off too much, but I can't do them back to back, say on 1:00; my chest feels like it is just going to explode. It's more like on 2:00!! Should I do them (or whatever length) with fixed rest for awhile, until I get used to it? Or on something like :15 or :30?

Or are the speed days race pace (likely ~2:00) days, and I'm swimming my LSD days too fast? I've been doing all of my swim work at about 70-75% MHR until now, which I think correlates with about 2:00 or so.

I've also found that I absolutely cannot swim with any effort if I am the only one in the pool. If there isn't someone else there, preferably in the next lane, that looks like they know what they're doing, I find it too hard to race the clock.