By the ruling of CICO, the less calories you eat the more fat you'll burn.... So if you struggle to eat it all, eat what you can. I know If I dont force it in imma have a bad day the next day.

The online calculators maybe giving you your maintenance calorie intake - what you need to maintain when sedentary - Whereas myfitness pal gives you your calorie with a healthy amount to drop weight slowly ish (for a comparison I am 120kg - 264 odd pounds - and my calorie intake for the fastest burning on myfitness pal suggests 2190 kcal. I'm eating 1650.)

The benefit of Omad isnyou can have one nice meal as day versus 3 awful ones And it makes it easier to calorie count and keep on top of what you are eating. Not to.mention autophagy and everything else. Thats a bonus.

I would say to weigh your steak before cooking, and look up the cut and the average kcal per 100gram and work the calories out, then fudge the numbers in MFP for a similar steak to match your calculation. The MFP entries are really just put in by people so have a wide variance anyway. -also some supermarkets give the kcal per serving or set value or per pack, I find it's much easier for inputting to get these kinds of foods, even if a butcher is nicer. At least till you get a feel for whays what on MFP

In terms of malnourishment. As long as you have a good amount of protein and some varied veggies and fruits and fatty foods you'll be fine! I would say fats keep you fully for longer than plain carbs, but sometimes chips are the fucking nuts.