The size needle hasn't much to do with the fabrics- the needle needs to be the correct size for the thread being used. Visit Superior Threads for free charts you can print that tell you what needle to use with which type/ weight threads and what the best application is.
Generally if your stitching is not good on the bottom your Top tension needs adjusting and if your top thread is breaking your Top tension might be too tight.
Clean your machine well, make sure the bobbin area is all cleaned up, oil if your machine is one you oil, rewind a bobbin, put together a small practice sandwich and see how it goes. Adjust your top tension a little ( loosen)
Sometimes the problem is the THREAD! When all else fails ( cleaned, I
oiled, new needle,( correct size for thread weight being used) , new bobbin) change the thread. It is always the last thing I try, out of frustration and 99% of the time fixes the problem.