Amount is irrelevant. It is not a specific amount but a pattern of use that is worrisome. Are there negative consequences (including a reduction of intellectial fuction and increase in restlessless when we are not using)? Are you using daily and never letting your head clear? Do the people around you express concern? Then you have a problem.
Marijuana. I believe in a perfect world no marijuana should be consumed. You don't live in a perfect world. I believe people obviously get benefit from marijuana. The question is always why are you using? For physical: then you should take just enough to make those symptoms better whether it's decreasing nausea or increasing hunger or decreasing pain. If it's keeping you from being active it's too much.