I could use more info here. Is your test naturally low or did you recently run a cycle? Or is it low because you have used a lot of gear on and off, and been on extended cycles? It sounds like you are commiting to HRT? I would suggest that you split your sust up into at least 2x wk plus how much ever adex you need to keep estreogen under control. When you do your 15 wk cycle, I would suggest that you split the test into EOD shots. So 1/2 CC EOD.
If you are commiting to HRT, you dont need to do a PCT. If you do want to maintain natural function, the first think you want to go is GAIN it back to begin with. So if your levels are low from gear, then you need more time off. With levels this low, you are hardly in the normal range and you are going to have a much harder time recovering. Actually, egardless of the reason your T is low, you are going to have a hard time recovering. And remember, if this is your natural level, this is the BEST you can do when you do come off. If you want to give me more info, I can try to help more