I'd delay on the Oil Painting for now. If you are new at painting, it will eat a lot of your time and attention just to learn to handle the paint. If you eventually attend an atelier, I suggest that you wait on painting and simply learn whatever the method is that they teach you... It is much easier to learn something if you don't have to unlearn all of your bad habits first.
Considering your busy schedule, drawing sounds like your best bet for now.
I don't know how long it takes for you to do an Old Master copy, but it sounds like you are breaking the speed limit.
May I suggest that you trace the drawing....and transfer it onto a quality drawing paper. Then in careful freehand do whatever is necessary to make your copy look exactly like the original (duplicate the proportion of the image to the paper size, match the colors, duplicate shading, etc.)
This isn't THAT easy and you may find that once is enough.
Please post a copy of an original that you are working from along with your completed copy and ask for a critique.
When you draw from life, be sure to illuiminate the model with a single source of light.
What anatomy/figure drawing books are you using? Some are certainly better than others....
Meanwhile, carry a sketchbook with you and draw, draw, draw...anything and everything when you can take a breather.
Good luck!