I would say the white spots are ick. maybe he also has some fungus infection. I use to have platys but every one that i had would die from bloat or from fungus and would end up dying. I stoped getting platys and moved on to mollys that would get ick or jump out of the tank. I currently have...
The part about him not being active and resting on the bottom of the tank is normal for betas because they usually are not active fish. Think about it.... when you bought your beta from the store do you remember how he was at the bottom of the cup or bag he was in?! The ones at my pet smart and...