If you are serous on keeping the most muscle you have put on. Before you do ANYTHING get a pinch caliper ( a few bucks at any pharmacy) and do a 7 piont skin fold at the least and find your BF % and LBM.
THEN you know what you have and were your nutrition needs to be.
If you don't, you are just flying blind and everything is guess work and hopes and dreams.
Would you just jump in a plane and fly to the islands? No you would do your research, know the plane, engine size, how much fuel you need, then fly.
Do your body and all your hard work the same justice. Get your BF% and find your LBM.
Then we can accurately help you out and not just shooting general fitness info out in the wind.