Ok so in the end I did have to brutalize a little the battery compartment. Whittled away a little of the plastic around the usb connector in the back to get my OTG cable to fit. Got the keyboard working and now the cfg was created finally. Now I just have the basic problem of controls not working as expected. Seeing as how the NES30pro controller uses the the d-pad buttons as axis controls and not as legitimate buttons, i need to get the axises to the cfg the right way.
I've seen people just switching to a Dualshock type in the controls menu but I'm missing this option as well. The troubles never end.