It sounds like you have a lot of confidence and work hard, which is great- keep it up.
However, taking 4 essay subjects along with fine art will really take its toll on you and won't work. I can tell you that fine art won't be relaxing with all the other subjects (not that I take it, but I have heard the workload is very intense). With gcses, you feel like you have security in understanding everything and you might always feel that you want to go above and beyond the workload you've been set. It's not like this at a A Level, and a lot of your time may be spent trying to understand the topics in more depth rather than just on memorisation.
You say that you're working for all this time every night, but there will come a point when it's impossible to do more work than you already are- all your potential free periods will be used up by extra subjects, and yet you will have more of a need for them.
4 is fine considering you seem to work so hard, otherwise I would suggest 3 is ideal.