Grats. That cage is the same ones I use for my baby sunglow and pied BP. You should be able to get the heat and humidity fine in there. Reread my post and use the cardboard and tin foil with damp paper towels and you should be golden until the snake gets to about 4-4.5'. Then you need to get him the PVC cage. that's funny about Hewitt Reptile as I used to go there a lot and knew the original owner before he sold to the gal which I know also but wont name names. Kind of surprised she was that rude as she is normally pretty mellow but anyways. The CHE will last way longer than a bulb and is much more durable. Boas don't need a light in their cage as room lighting will work just fine and in glass tanks where you want to keep them mostly covered, its hard to set up a light in there.
Now one more piece of advice, like the reptile owners bible, go to Home Depot and buy a temp gun. Then you can use that to dial in the warmest spot under the CHE with the lamp dimmer. That's what I use and I got both my sunglow and BP set with 87-88F warm side, 81-82F cool side and 50-60% humidity. This is in a 75F house but it gives you an idea of what you can get and that's with the dimmers oly set about 50% so if your house is colder, you will have plenty of room to play with. And I too use the 100 watt CHEs.
Oh and also you don't have to feed F/T. I personally feed live that I pre kill beforehand since I prefer to feed all my snakes fresh but if you are squeamish about killing rats/mice, then yeah probably go to F/T as feeding live isn't really the best option imo.
Oh I also forgot to mention, you don't NEED a UTH. I never use them. As long as the ambient temps are good in the cage, a snake will be fine. Just set up one of his hides under the CHE so the CHE warms it and if he really wants heat, he can sit on top of it. That's what my sunglow does and I use Reptile Basic hides as they are cheap, nice, and offer a flat top which doubles as a spot to lay moist paper towels on under the CHE and the snake sometimes likes to sit on the warm moist paper towel lol.