Hi

There is equal weightage of chemistry and physics in NEET UG exam. If you think that you can score passing marks by just doing biology portion then you are wrong.

You are well aware of the increase in competition so you have to work on your weakness in order to gain confidence for the exam.

The only way to increase your score in chemistry is to go through NCERT and practice more questions

For physics, you can go for coaching notes or any reference book to build your concepts.

There is no golden rule that you have to refer certain number of MCQ books. Stick to standard books  and practice more.

Keep solving previous year questions, it will help you a lot.