Inky, 3 gallons is not enough soil for the size plants I grow. I would suggest using as much soil as you can/flower them out a little smaller. I think your base mix and amendments looks good! Peace! P-
loamy is good, but be mindful of the sand and compaction easy on the cow shit worm castings FTW not a fan of peat, but if need be top dress with mulch (wood chips, pine needles etc.) easy on the lime or you will get hot conditions, a sativa might like it though kelp for sure ph the black topsoil just for kicks favor the vermiculite, perlite is prone to compact and dust up, but nice for the upper layer easy on the salts and flush well near harvest if you use the epsom might try the fish emulsion as a base for tea \nbone meal - yes rock phosphate - yes for early veg and late bloom ... you might consider a bit of rock dust, glacial dust or maybe even some azomite
Hey Inky! I never sterilize pots. As long as they don't smell bad or anything, I'd think you'd be fine. P-
I'd probably ditch the topsoil and replace it w/ some really nice compost or at least dig up the topsoil yourself. 2 cents