To me it sounds totally impossible...even people who are cutting eat more than 1800 calories each day...And you have gained as well as maintained 10 pounds of muscle through it all? If you do follow such a regime it doesn't sound too healthy to me, because with 1800 calories you can't possible be ge...

Your diet needs to be reworked as well. Eating most of your daily intake of calories during dinner doesn't sound very good to me. You should try to spread out your total intake evenly throughout the day.