I'm so glad he's eating!!! It sounds like your frog may be like mine and just not recognize the pellets as food. It does tend to be tougher on gravel, as they fall in the cracks. . . If you can't get him to take the pellets, you might want to consider getting another type or two of frozen food for him. LOTS of people feed bloodworm daily with NO PROBLEMS, but I've also read that it has been linked to bloat when fed exclusively. Totally your decision to make, of course, just wanted to point out what I've read and heard from others. Either way, be sure to WATCH him while he eats. It is really important that you make sure he's getting enough - and not too much! The frog's belly is slightly to the left side. You will be able to see it round out when he has had enough to eat if you pay attention.
Good call on offing the lights, leave them low for a day or so to let him settle in. He'll like it, especially since he's noctournal, and there isn't very much for him to hide in. The pineapple he loves, I bet. . . my frog has a 'house,' too - he loves it!
Hornwort is an EXCELLENT idea. It can be a messy plant, but it's one of the best at soaking up toxins in the tank. In a small tank, this can be a lifesaving plant! Plus. . .your frog will DEFINITELY love it, and will feel much more comfortable with the extra shade/security of more plants. It grows very quickly, so you'll have plenty to share among tanks before long!
I agree that you should wait on frog #2. You're overwhelmed right now because you're learning about an entirely new and different species - AFTER bringing it home! I've been there - just a few months ago - it isn't fun, but I think you're on the right track. Get your frog settled, eating properly, and comfortable with maintaining his tank. . . once you are comfortable with frog and what he needs to thrive. . .you just might change your mind and be wanting a bigger tank and a buddy ;)
For now - good luck, keep us posted!