First step - eat more. Eating at or below your calories is not going to help you recover in time. And you certainly won't get stronger.
My wife is an RN (cardiac ICU), so i know what she goes through and through her can relate to the schedule.
My first recommendation would be to add a high quality post-work out like the Surge post-workout formula. This will do 2 things for you. It will increase your calorie intake and it will speed recovery.
Second i'd say evaluate your time and consider some changes to your daily schedule. Clearly you're not interested in bulking per-se (as you are already willing to eat below your calories. Read the time-restricted diet article that T-Nation posted recently. Maybe you can use the principles from that to ensure you're putting on lean mass and the "time restricted" might fit well with your schedule.
Like i said, through my wife I can relate to the 12+ hr shifts (13 including handover from day-shift) and J-CAHO restrictions and having trouble finding time to eat. This might lend itself better to a liquid lunch. You could try a protein shake made. You can find some recipies that arn't just powder and water to make it more calorie dense and filling - i always liked using milk and cottage cheese blended together with chocolate Grow!. Sometimes i'd even add some plain oatmeal in too. (geez, i might as well be on T-nations payroll since i'm pushing their products. They are the best i've used though).
Bottom line - Eat. Find a way to increase your calories. Have a huge breakfast and Huge dinner and a protein shake for lunch (kind of a paleo thing). Night shift should be a little easier to find time to get at least a liquid lunch.
Also, your sleep is probably crap because you're on night shift - do some day-off prep for the rest of the week so you can get more sleep. Maybe add z-12 to help get better sleep. Sleep is when you recover and grow. You could try to get on day shifts but that would make the eating thing more complicated.
One last thought - you could try throttling back on the workouts. This would reduce calorie requirements and recovery time. Once you start getting stronger again, gradually increase workouts to match your your eating/recovery.
Keep us posted.