Ditto. I'm sure you and others realize that given its length your post is highly scrutinizable, but if you replace "must" with "may", I did like your statement in italics as food-for-thought:

If we can feel real inside a non-magical computer simulation, then our feeling of reality [may] be due to necessary properties of the information being computed, because such properties do not exist in the abstract process of computing, and those properties will not cease to be true about the underlying information if the simulation is stopped or is never created in the first place.

... though my thoughts will have to eat it awhile longer before I digest and judge it as an actual idea :)