1. There are too many things unknown about danzo's guards for me to give you an answer. Even if time went the same speed in the kamui dimension, they would have died anyway. Tobi most likely fed them, and so that is just a matter of how often.Tobi's time travel is the key to unlock all mysteries, assuming that your theory is reasonable ( I think it is) and relying on the fact that Kamui's dimension is parallel to the real naruto world dimension the question which pops in every one's head is how does tobi teleport from a place to another?, I don't think the answer is that there is a difference or a variation in the time rolling process between the two dimensions because:
How does the shinobi being locked in Tobi's dimesion survive for example like Torune he should've died for many reasons like hunger for example.
Another questions is:
How does Tobi locate the moving targets that he wan't to travel to like for example when he located sasuke during the time he was heading to kotnoha and locating minato who teleported with his FTG, this locating process can't be done from the normal dimension because if he locates a moving target and teleports towards it he will actually appear at a place behind the current location of the target but Tobi actually appears before his targets.
So the only explanation of his time travel is that Tobi has somehow kind of control over his Kamui dimension which he locates his targets from and then teleport like super fast in his dimension towards the place parallel to the place of his target, or maybe in Kamui's dimension there are space time portals which teleports him the location parallel to his targets' in normal dimension.
Sorry if I didn't make it clearer.
2. I have no idea how he locates people with kamui, but that is not a variable in this theory. Unless you can relate that to time. Ignoring HOW tobi is able to locate people, if he were able to he could also just travel through the kamui dimension and because of the time difference he moves faster than through the normal dimension, by a significant amount.
3. If there were anyway that tobi could move into the dimension in a different place than the parallel points which he is in, which would be necessary for the teleportation part of your theory, then he would do so to avoid the attacks from when kakashi sends things through kamui. As for your space time portals within kamui, that is a possibility, but I believe it is a less rational one. It is not likely that it would be possible or easy for tobi to know where each portal would lead him, because I dont believe tobi would be able to create these portals. Therefore he could risk missing where his target would be and wasting time. Also how would he locate his target through a portal?
I believe that his ability to locate people comes from his zetsu body parts (or at least his body parts akin to what zetsu looks like) and he is able to locate people through the same method as zetsu, but he doesn't have the control over hashirama's DNA to move through trees, so he uses his own s/t ninjutsu to reach there.