Some help with rocket/nuke math please

So I've been doing some research for a book and I came across some stuff that doesn't look good for real life.

The NK rocket makes a polar orbit every 93 minutes. Leo at 99miles is 88 minutes and Leo at 1200mi is 127. Just estimating but that puts their "satellite" at 250mi does that sound about right?

Then I thought back to the last NK nuke test. If it was an H bomb at 10KT the gamma should be on par with a 100KT bomb or thereabouts. Does that sound right?

Going back to the big picture if there is an exponential increase in their nuke test they should have a 5-10MT nuke in 8-10 years. That would be enough to take half the US out with an EMP.

I'm not saying that's the realistic timeline but if you disagree with the math please say so. It would put my mind at ease.

Oh and I found this which didn't help

[link to mobile.wnd.com]