As far as I know, there isn't a maximum word limit, but like mentioned earlier, the more you write, the higher are your chances of making mistakes and also you would end up losing time if you write too much. Also, you might be having issues with your task 1 rather than your task 2, which could be affecting your scores. I have read many test takers' stories where they got better scores when they started concentrating and working towards improving both their tasks, rather than just the essay.
I would suggest to take a break, get a good tutor (there are several really good online tutors, though they are not free), practice for a month or two (depending on how much you need to improve) and then give the test. It would be a waste of time and money to continuously take the test without being able to find and correct the problem which is holding you back from getting your desired score.
There is also a FB page where the admins give free reviews for the writing tasks you post on the page. The group's name is "IELTS Tips & Tricks", do check it out.
All the best!