There is no need to force feed yourself, if you can’t meet your calorie target with 1 meal without eating junk, just add a snack (20:4) or a second meal (18:6) there is nothing wrong with that.
Also with fasting stomach has a tendency to shrink somewhat, so it might become harder to eat big meals.
You could also consider ADF (36:12 or 40:8) or 1 day OMAD, 1 day 2mad, there are no downside to mix them up as long as it is more sustainable for you.
Any reasons why you set your mind on OMAD in particular?