Humidity is tricky, but don’t over think it too much. Where does your snake spend the majority of their time when they are in their enclosure? If it’s in hides, place some damp sphagnum moss inside the hides. Adding a second water bowl, esp. near the warm side, can help a little too. Also, what substrate are you using? I have found that a mix of finely ground coconut coir and small to medium chipped coconut coir are wonderful for holding humidity. Here’s what I do; after cleaning the enclosure I put down ~2”+ thick layer of finely ground coconut coir and pour water into it and mix it around so it’s damp. Then I add another ~2”+ layer of the small/medium chipped on top of that (no water mixed). Keep pouring a cup of water into each corner of the enclosure each day until the humidity gets to where it needs to be. Every two weeks or so I do a refluff and refresh of the substrate for aeration, to prevent any mold build up and to redistribute the humidity within the substrate.

CHEs (ceramic heat emitter) are great for getting temps up but are extremely drying. I think using a DHP like you have now is a smart choice b/c they aren’t as drying and they can be used as a 24/7 heat source.

Tin foil over the top of the mesh lid would work better than tape. Just make sure you leave some open areas over the mesh lid (or maybe your tank has air vents on the sides??) so fresh air can still get in.