Can someone help me figure out my calories for weight loss?

I weigh 250lbs and I’m 5’8. I’ve gone from sedentary to lightly active for the past 2 weeks by adding daily exercise. I do a low impact (bad knees), but high intensity cardio workout for 35 minutes every day to burn 300 calories. I use an Apple Watch to monitor my heart rate for accuracy. 2-4 times a week, I’ll burn an extra 300 calories by doing something else active. I’m planning on adding light weights to my cardio workouts and would love to deadlift as well, but am restricted for the time being. I have a minor surgery coming up and will not be able to do squats or heavy lifting. They say I will be able to continue cardio. I am totally confused as to how many calories I should be consuming and if I should be eating the same calories regardless of exercise? I read that burning 3500 calories to equal a pound isn’t accurate...I’ve noticed! I estimate that I was eating about 4000 calories before this and have cut down to 1500 calories, but with a very slow loss. When I eat more than 1500, I seem to lose a little quicker. I’m just trying to find out where I should really be for optimal weight loss and I’m so confused with all of these calculators out there. Can anybody help me figure this out?