one of the most important things you can do is get a good gradient going...its surprising how a gradient will change a lot of things for a reptile. Make sure its a gradient controlled by a thermostat and at least for my bps I use a under tank heater (UTH) for belly heat....bps really should have belly heat.

it very much sounds like he needs food....ill leave the food advice to someone better versed in snake rescue. BPs are very hardy little guys...I would NOT add anything to water personally...remember 2 hides that are snug...1 on cool side and 1 on hotter side.