Yeah it does, but i mean i feel i've ruined the chance now to work with him by saying is it ok to get a part time job aswell as this to earn some income.
Time to man up as worrying about it isn't going to get you anywhere. Tell them you really want the job, so you've taken part time work on your own time that won't have any impact on you shadowing them/him.
If that doesn't work you can't say that you didn't try. It'll be their loss and they were treating you like **** anyway.