So far, you seem to be doing a good job with the enclosure.
What are your temps without using the heat mat? From the pictures you posted it seems your thermometer reads 74/75ºF. If that's the case, once you have your heat mat running you will most likely be able to maintain proper temperatures.
However if one heat mat is not enough to achieve proper temps, you can use a 2nd one on your cool side and set it to 80ºF. That way you ensure your slithery fellow has the proper temperatures all the time.
You might want to start thinking about covering, at least, 3 sides of that tub since it is a clear one and ball pythons aren't really fans of being exposed.
Now some questions:
- Do you have that heat mat plugged into a thermostat? If not, don't use that heat mat until you have a thermostat for it or you will most likely burn your scaly buddy.
- Where is your thermometer probe placed and your thermostat probe?
- How big is the male you're gonna get? (His weight)