My question: am I allowed to eat a big meal after a heavy workout?

Information: I am 5’9 weighing 160 pounds looking to lose weight and gain muscle mass. I am currently on a caloric deficit of about averaging 1600-1800 calories per day.

If I go to the gym without eating anything, am I allowed to eat over my caloric deficit limit, and how much am I allowed to go over by?

My plan for the workout:

30 minute 5mph treadmill Bench press, dumbells, abdominal workout (leg raises, push ups, etc) 3 minute plank to finish it off

I’m estimating that I’ll probably be working out out (minus in between breaks) about 2 hours, I typically only work out for 45-60 min.

With that being said, how much calories should I be safe to eat in this big meal (which will reach my protein intake since it’s a buffet diner) without risking fat gain?

I plan on making this my only meal of the day as well.

Thanks!