HCG should be all the way through cycle and ceased only 2-3 days before pct, possible danger from HCG is some desensitation- but thats where clomid/nolva step in.
As for AI dosing, thats difficult as it depends from person to person, some people need very little, almost nothing, some people need lot.
In pct I would not use anything that can affect hormones, sometimes peole do get away with bit of DHT sometimes not, why risk?