Yes to the calcium/vitamins. Use a calcium supplement with D3, I'd say, for your frog's size, twice a week, the vitamins every two weeks - at least that's the regime for adults. Your's probably isn't fully grown but at the size you described certainly isn't a froglet. Never use the two on the same feeding however.

Earthworms (specifically Canadian nightcrawlers) are a great staple food, perhaps the best available. They're the preferred frog food for both me and my Pyxie. As for how much to feed, Frog should stop eating when it's had enough. Otherwise, you can monitor its weight and adjust its intake as needed.

You should feed him pinkies no more often than once a month, if you still wish to.

And if you haven't already move the heating device onto one of the WALLS of the tank. Otherwise undertank heating devices should never be used for these frogs, as they burrow to cool off and will cook themselves.