"Apparently there's no medical text supporting the belief to start slowly with iodine, and you can jump straight to 50mg? And is it safe to stay at 50 mg forever?"

-This forum is not medical or scientific; this is all about self experiences with Iodine & co. Most here have chosen to take responsibility for our own health. What we recommend are based on that.

That said; I plan to stay on 100 mg of Iodine for some time, how long I dont know, forever is a long time; I cant possibly know. This amount is for me just to keep the other halogens, fluoride / bromide, at bay. Then radiation and toxins in general.

"If not, how exactly I go about increasing it and do I have to divide it into multiple doses? (Like take 1 drop a day for 1 week, then 2 drops for another week, until 8 weeks in which I get to 50mg, then remain on that for 6 months like Dr. Brownstein recommends, then wean down a drop each week until I'm at 12.5 mg?)"

You seem to complicate things. Just get it in there. If you want to go slow, do it. I did, but I would have jumped straight into the 50 mg +, if I know what I know today.
Or, follow Brownstein if that feels safer. Your choice.

"Also... will it interact with any of the following vitamins I take, if I take it at the same time, and can it be taken with salt foods? (I use Kalas iodized Sea Salt )"

-all elements interact with each other. In the beginning I seperated selenium from iodine, now I dont bother.
Of course it can be taken with salt foods. Salt will be your friend in the time to come.
You will need to do some reading; here is a start;
//www.curezone.org/faq/c.asp?a=13,281,2962


Only one comment to your supplements; make sure the selenium is the methionine form. And; take magnesium without the calcium. And up your salt!!! Real salt; I am not familiar with the one mentioned. Maybe others are.

I think vitamin C will convert Iodine to Iodide on contact.