Vox

Background info: 22 year old male, 87kg, 175cm.
My lowest weight was 78kg but I regained over the past couple of months due to relapsing back into old habits. Been back on track for the past 5 days but I can't figure out how many calories I should consume daily.
There are plenty of online tools that help you calculate your TDEE based on gender, age, height, weight and activity level. Based on my information I should consume around 1550 calories per day to lose weight fast, and around 2000 to lose weight. I currently have no problems getting to those numbers, but they still feel a bit high for someone who has had weight loss surgery. I also hear of people having drop all the way below 1000 calories to lose weight.
This makes me uncertain whether the TDEE is the same after weight loss surgery. I can't find any information about this online.

The eating part at least. I still had a lot of bad habits post-surgery that I never sought help for. Oftentimes I don't stop eating until I'm satisfied, but until I'm full. I think this has resulted in my stomach stretching quite a bit, because I was astonished today when I found myself able to eat 3 whole sandwhiches with scrambled egg. I am fairly certain someone who's 9 months post-op shouldn't be able to eat that.
Despite this, I'm still 54kg (120lbs) down, but I know that if I don't fix these bad habits, I will start gaining weight again sooner or later. I feel like an enormous loser now, but I want to turn my eating habits around once again.. I just don't know where to start. Any advice is welcome. Thank you.