I've pulled fronts of fmy N tractors that use 4$ tubes.. and found patches /forums/images/graemlins/shocked.gif
I did as you did.. wire wheeled the rim.. hit it with a rust stopper primer, then painted it liberally ( many coats ) with an appliance epoxy enamil i had laying around. Like yours.. came out smooth, with some evident pitting.
I put the tube and tire on and it has been that way for 2ys now. If the pitting bothers you, you can use just about any type of sndible filler then repaint for a smooth finish.. however.. once you get the prickly stuff out.. the tube is much happier, even if a few pits remain. On my worst rim, also a front.. there was alot of welding and brazing .. whole lotta pitting.. I use the old tube as a boot.. just cut the sides and middle out... that's holding air now as well..
Sounds like yours will be fine. ( Learned the duct tape trick from a tire guy (among others ) that services alot of farms... he took a roll out on farm calls.. said sometimes the farmer didn't have time to 'fix' the rim.. so they did the duct tape thingy as a stopgap measure.. )
Soundguy