Rule of thumb is:
10% of your weight for 3mil wetsuit
10% of your weight plus 6lbs for 7mm wetsuit & drysuit
At least that will give you a starting to either subtract or delete weight until you're properly weighted. There's no real way to truly figure out your dive weight because everybody is built differently.
A lot of people say this, but in my opinion it starts you off much too heavy.
The OP is 215 pounds, and he was apparently fine with 16 pounds with a 5 mm farmer John plus a shorty. That is more neoprene than the 7 mm in that formula. According to that formula, he should have had nearly 30 pounds--or more--instead of the 16 he actually needed.
I am a little smaller (not much) then the OP, and I think I would have needed about the same weight he did for his dive. I assume we have similar body types. When I dive salt water in a 3 mm suit, I need about 8 pounds. That formula would start me off with 2.5 times as much weight as I need.