Hello there!
I have a Nikon D3300 which I use for astrophotography, now I realise you've stated the D3300 does not support bulb mode, but I managed to get it working fine with mine using the command scripts on the right hand side of the bulb window, at least I had the options of "bulb capture" "phdguiding" and "wait"... the "loop" command unfortunately doesn't seem to work...
So, my question is, can you get loop working? Or if not put in a check box or something that gives the option to loop instead?
Many thanks.