Call It Quits with Glass Terrarium or try Heat Mat as Supporting Heat?

Hi, I recently got a glass terrarium for my BP thinking I could DIY it into containing enough heat. A week in, and even though 3 of the walls are covered by inch thick foam, the top mesh is covered by HVAC tape, and I have heat lamps on both sides of the terrarium there is still zero gradient and the ambient temp is ~80 everywhere except under the heat lamps (even though they’re flood lamps). I hear a heat mat with a dimmer underneath the cage can help with ambient temps, but I’m also wondering if I should just call it quits here and try to resell the cage & buy a PVC one or if it’s worth trying to make it work - and, if it is worth trying to make it work, is there anything I can do besides a heat mat underneath to further keep the heat in?

Pics are for visibility and as payment for any advice lol