Did you ask the previous owner if he was eating live or frozen/prekilled? May sound stupid, but if he has fed on frozen his whole life, a live rat might scare him.(Like I said sounds stupid, but ball python are very timid and shy, they can actually become traumatized into not eating live if they are attacked by their rat). aside from that as stated ball python can and will go off of food randomly, or because of stress from a new enclosure or new smells. they can also go off of food for a LONG time. I've personally seen a perfectly healthy bp go off food for 11 months, and then randomly start eating like a champ again. Also as stated, live rats can just be dropped in and watched to make sure there's no damage to the snake, if you want to dangle food by hands or tongs I would suggest frozen or prekilled.
I would personally bump humidity down a bit as well. 40 to 60 is good for them, prolonged exposure to too much or too little can cause problems like respitory infections (low) and scale rott (high). A lot of Condensation generally indicates humidity is a tad high.
I don't use tape or under tank heaters, but it's recommended that if you do, you hook it up to a thermostat to prevent overheating.
Congrats on the pickup btwgot any pics yet?