Is my 29gal overstocked?

You are definitely overstocked. Your first answer telling you a rule of thumb is definitely correct. It is one inch per gallon and you ALWAYS need to go buy the fish's adult size not the size they currently are.Mollies get to 2 or 3 inches I believe so they alone should have a minimum of 16 to 24 gallons which is almost your entire tank. Gouramis size depends on the type because there are several dwarf guaramis but even they need a minimum of 3 gallons each. So yes seeing as I have only talked about 2 of the 5 types of fish and numbers present in your tank I would definitely say its overstocked and possibly try moving some to another tank or even donating them.