I can't answer your question about whether this is a normal level of fatigue. Probably too early to tell, so give it a little time and see what happens. If you're doing it right, there will be fatigue, but you should be seeing fitness gains and the ability to keep going despite the fatigue.

I'm probably in roughly the same place as you fitness wise, though not overweight. My experience with TCC (intermediate commuter program) is that the frequency of interval sessions is a bit too much for me to recover on a week-to-week basis. Over the course of the cycle, excessive fatigue accumulates for me. My body just doesn't recover from hard efforts like it once did (I'm in my mid-40s). I'll probably do it again at some point this year, but cut back the number of interval sessions to about 2/3rds of what is recommended. You might experiment with doing some cutting back as well if your fatigue accumulates rather than becoming sustainable. (Don't know what to recommend specifically because the programs are structured differently). You should still see fitness gains if you cut back - I don't think you're wasting your time in any way if you don't do 100% of what TCC tells you to do.

I'm not trying to be discouraging. You might find that this is just a little hurdle and you can do the whole program. Just listen to your body. If you cut back, cut back on the number of sessions or the number of intervals in a session, but not the intensity of any given interval.