Greetins everyone, thanks to the people who answered me in DMs, specially Lotus for all the good advices, here's a sum up of what I plan for now and additions infos :



HRT
My lab work 1 month ago, I was still using gel :
Estradiol : 62 pg/mL
Testosterone : 0.52 ng/ml = 52 ng/dL
I know that estradiol was clearly too low, while my testosterone lowered a lot (668ng/dL pre HRT), which is encouraging. 
This is why I switch to estradiol injection. 
I should reach an average of 300pg within a reach of 350/250pg of estradiol, given how my testosterone lowered with only 60pg of estradiol, I hope that I won't need an anti-androgen, we'll see next lab test.



Breast pumping
Apparently HRT start and breast pumping are compatible.
I'll base my strategy on HelloDidi excellent tutorial, hope to manage to do it 3 times per day, we'll see.
https://www.breastnexum.com/showthread.php?tid=31273



Supplements
Supplements I'm already taking are :
- 20mL/day Fish Oil (good fat for Omega 3)
- 10mL/day Cod liver oil, good for vitamin A (no impact on breast growth to my knowledge) and vitamin D (can help growth hormone, 10mL = 800UI approximately)
- 500mg/day L glutathion (no impact IMO)
- 300mg/day L cysthine (no impact IMO)
What I will add for additional breast growth :
- 3g/day MSM