no offense, but I'm starting to loose my patience when i see something about "experienced frog keepers from a pet store", sorry.

Luke, you are keeping your frog in a small enclosure, on wet papertowels with a heat pad attached to the bottom, take the heat pad out asap and stick it to the side or find some other way to heat the enclosure. what you're doing is very dangerous to a frog.

based on last pictures it does seem like MBD, there is only one way to confirm is to take him to a vet for Xrays, but i suspect it might be a bit different story as well, i goggled the vitamins you're using, they contain 20% Ca, traces of vit D3 and very low on other vitamins. would you please check the contents of your bottle and post it here ( or pic would do), i couldn't find a reliable source for that. too much Ca with luck of vit d3 and other vitamins can lead to opposite of what you're trying to achieve, too much of anything is no good, it is all about balance.

you're saying you have a frog for 4 months, how big is a frog right now?

so let's figure out what are these your vitamins, and if i were you i would schedule an appointment with a vet to figure out if that is MBD and continue accordingly.