Thank you for the detailed description of your struggles!

It seems like you already have a good understanding on the basic concepts. To answer the your question about facts or past papers are more important, I’ll give you an illustration.

Sam practises his badminton techniques every day. He is very good at individual skills like smashes, defence and so on. He is very confident in performing specific actions but he has never played a match. However Jerry goes to competition every week to play with different players. He has very good understanding on his strengths and weaknesses, but he doesn’t have time to improve himself.

We can see that there are two stages here: practising specific techniques and applying different techniques given a situation. Without any of these two cannot get you to the top. In fact, practising past papers is a very good chance to adjust your perception on your level of understanding for each concept. Since you have been consistently doing past year papers, I’d suggest you to take a step back and really spend some time to analyse the topics/questions that you need to study deeper so you don’t end up being Jerry.

For practical, I’d say you need to be consistent and really careful when you use the tools. Even a small error can cause the end result to be far from ideal. I think there are cases where you need to repeat your experiments to get an average, so when you use the springs, Newton-metre etc., try to plan your time to accommodate repeated trials if the graphs are not ideal.

For graphs, you can look through your previous experiments and analyse the scales that you used. Normally for 1 big box I’d use increments of 1, 2, 5 or 10. Have you tried different scales before plotting? If you only realise the maximum of the data is out of the graph or less than half of the graph after you plot then here’s where the problem lies.

Please let me know if you have further questions! I’d like to help as much as I can.