Yes I do separately and together I'm just unsure of how exactly to fix the problem unless I play them really really slowly!!!
Part of the problem is that your technique is simply not developed enough at this stage. But finger indpendency is a vast problem even for accomplished pianists. You may want to consult the 4,5 finger-independency-thread in the performance section.
If you want a "quick fix", then I think you are on the right track. Send your pride and musicality on vacation for a week. Just play the invention about 10 to 15 times every day very, very slowly as if it were "Adagio" (if it takes you less than 3 minutes to play it, your are way too fast). Do not even think to play it at tempo during this time, same with the scales. Chances are that, when you speed it up again in a week, you will be surprised.