Any way you can get ahold of an additonal anabolic like dbol or NPP? I could see doing a solid 12 wker, starting with prop and (something for more mass gains), then switching to the andromix to harden up. I would also add in a low dose of an AI to help control estrogen and therefore help fat loss through the process. The key will be your diet, eating very clean, but getting a good amount of cals. Of course, I cant say how many cals you need, since I dont know your body, but at 20% BF, I have to think that insulin/carbs may be a concern for you. I can't imagine you wanting to start with over 300g carbs in the diet. Make sure you get them from low glycemic sources like brown rice, oats, sweet potato.
Heres what I'd envision for a cycle. You probably wont use all of your gear, but keep in mind, your body is super clean right now...one benefit of your 3 year "break" ;) So try not to judge yourself by what you used in the past. You can probably make great gains on much less than you used to use. Take advantage of that.
12 wk cycle
adex as needed throughout
prop 600mg EW
dbol 30mg ED
1cc ED Andromix
.5cc ED Prop
you'll obviously hold more fluid in the begining of the cycle and dry up as you drop the dbol. overall, the mg of hormone will increase in the 2nd half of the cycle,which I personally find helps me to avoid homeostasis
PCT starts a few days after last injection