Big guy looking for help

When I started I was 6'2" 370 and the app said I needed around 3500 calories a day to maintain. I started to cut back to 3000 per day and noticed a fair amount weight loss those first two months. I just kept gradually reducing my calories. Protein wise I've heard anywhere from
. 8 grams up to 1.5 grams of protein per pound of lean muscle.

I’m 6’2” and started out at 305lbs. I personally would try 2500 calories and see how that works for you. That is close to your bmr ie how many calories you burn just living so it tends to be a safe sustainable starting point for most people. If you feel like you’re starving yoy can always add a few more calories or if you’re not losing cut some I would try 100kcal increments. As for the protein issue there is a lot of debate over how much one needs, according to my doctor if you’re getting at least 40 grams you’ll be fine. The basic dietary guidelines is .8 grams per kilogram which is roughly 115 grams @320lbs. Weight lifting and gym lore and some research suggests .8-1.5 grams per pound since it is shown to minimize muscle loss while in a calorie deficit, however this can be hard on the liver if you have any health issues so I would discuss it with a qualified health professional first.
To help you make a decision of what is right for you find out what your bmr and tdee with an online calculator and use the mfp suggestions as guidance for finding what is right for you.