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If the water is dirty, you should drain out the dirt. Other than that it shouldn't need draining. We don't want to add more water to the boiler than needed, since a lot of fresh water will shorten its life.

1" is more than adequate to vent the air as fast as the steam can heat the main. are you measuring from when the boiler starts steaming? it will be a lot faster when the system is still warm from a recent cycle than from cold. you can take the vent off and run the boiler until steam gets there, it isn't going to get any faster than that with a bigger vent.

others will know relative sizes of different vents.

After reading @EBEBRATT-Ed's earliest post, I have this doctored photo that is be the easiest fix for you @RCooper.

@bdl as @ChrisJ mentioned total up the rad EDR and compare that # to the boiler nameplate. Don't add anything

The EDR rating on a boiler includes the 33% pickup factor.

I'd never exceed that rating my self. IE. if the boiler's rating is a hair under, do not go to the next size bigger, it's a mistake.

Or go with a different brand boiler. For example the chart posted above the Peerless 63-04L is 383 Sq. Ft. if that makes you more comfortable.

My old 300 Sq. Ft. boiler and 347 of EDR works fine, even when it is below zero Fahrenheit outside.

I’d go with the 350.
you can always tighten up the envelope if needed