As long as your club is running the POTD or an EC party like cat cafe or Dog Star, you should be getting your hunt drops from there.
Yes, hunt drops from parties and cash payout increase as ur cs increase (make sure you're at max plunder, i.e. total tut worth shd be 15m/1kcs or 15b/1mcs). Also, as ur cs increase, the no. of hits you'd need to get max party drops will decrease
I worked out my Max plunder 116 x 15m = 1.7b but I have 3.9b and my plunder can still go higher? Has the 15m changed?
You don't. It's outdated and shallow advice. Odd-tiered dormies give the same stats for your buck as even-tiered dormies. The most important principle to follow when upgrading is to skip tiers. But better than going full even or full odd tier is actually to go half and half. Half your dorm is even, half your dorm is odd. You upgrade your left half 4>6 then your right half 5>7. Left, 6>8 and Right, 7>9 etc. This makes for a much smoother and more effective upgrade pattern than 5>7>9>11.