Thanks for the advice. I'm using bruiser CA but he has the Avengers alt, and I haven't decided if I should spend 48 CP for WWII bruiser (got tact already) just to farm 12.2. However, WWII bruiser Cap might make it easier for me to farm 12.2 in Challenge Mode, as it is a chore to do it with the Avengers alt.
Btw, it appears that after you finished researching Synethesized Antidote from SO10's task 6, you can buy and sell them back (at a cost of 200 silver & 4 SHIELD) for 10,000 silver. Someone from the forum claimed that he spent 4,000 SHIELD and made 10 mil silver. I still haven't finished with the research, but since I have over 15K SHIELD I don't mind converting at least 1/3 of it into silver.