Is 420 calories too much for breakfast?

This depends on you, and what you are trying to accomplish. If you are happy with your weight, or trying to gain it doesn't sound like that much.

If you are trying to lose weight there might be ways you can lower it and still be satisfied with breakfast. For example, a cup of plain oatmeal is only about 160 calories. Adding a cup of 1% milk is about 100, and a piece of fruit like banana, or apple adds another 100.

That small reduction of 60 calories will add up over time. About 1 pound weight loss every 2 months without any other change on your part. There are other fruit options you can eat to lower your breakfasts calories, if calorie reduction is your goal.

No. You can lose weight on 1800 calories per day. 500 each for breakfast, lunch and dinner, with 300 remaining for a snack.

no.

If you are dieting thats a good amount

No its not

I eat 1,000 calories
5 eggs, 2 bowls oatmeal, 1 yogurt and 1 glass milk.

No! You need to have most of your calories at breakfast to be energised for the rest of the day.