Worth another try? Fungus gnats, stunted, and over watered?

It's a photoperiod so you could get it back to health, then flip to flower. It is only in flower if you gave it a long enough dark cycle (and continued to do so). You'd know if it is. Bti will take 2-3 weeks to wrangle an ongoing problem. yellow traps would help kill th emature ones, but they are more of a nuissance at that stage of life than a problem. The larva is what cause the damage. You should be able to get it back into shape faster than any seed would get to thes size this plant will be in 2-3 weeks even if growing a bit slower while stressed. And, just for learning, if new.