I don't have experience with racks, so I'm not familiar with the specifics of the rack you're using.
But, I know people use back heat as well as belly heat on some racks. Is that an option with yours?
That would allow the back heat to raise ambient temps while using the belly heat to supply a hot spot.
Again, I'm not familiar with that specific rack (although I see it used by many people) but if this is an option it may solve your problems.
Like bogertophis mentioned, this is why it's so important to be prepared before bringing the animal home. It's a HUGE part of keeping these amazing animals. Having your equipment set up, dialed in and running saves a TON of stress in you, and more importantly, the animal.
But, this is how we learn. You'll be all set up and ready to go before bringing your next snake home
Any which way, time is of the essence here, so you'll have to figure something out sooner than later.
Good luck, please keep us posted and don't be afraid to ask any questions you may have.