That's some good feedback there! Far better to have something to work on, and to know where you went wrong, than to have no clue. It would be far worse if you got a really low mark for a TMA, with no meaningful feedback whatsoever.
Long story short, learn to love feedback. It is how you improve. Without it, you have no idea what your weaknesses are and what you need to be working on. Getting deflated about it is only going to make your experience a miserable one, because feedback becomes much more critical in levels 2 and 3. By then, you are expected to know what you're doing. You will need a much thicker skin.
Also, don't forget that your tutor is there to help. If you feel you are having trouble staying on topic, ask them for advice. They know your work better than any of us, so will be able to provide much more specific suggestions.
As for referencing, they are not going to be overly strict on your first attempt. You do get a fair bit of leeway at first. However, it is important to clarify with your tutor if you have any doubts. Furthermore, the module website will give you the standardised format. Always best to stick to that so that it becomes second nature. Each tutor may have their particular idiosyncracies, but if you stick to the OU standard, you have yourself well-covered.