The reason for cutting the 150/300 was due to chip color up. But you would actually need them for 2 more round because of the 50 and 75 ante. I don't know.
I don't think that adding the 2500/5000 means you need to have a 250/500 though I just thought a smaller step at that higher blinds would be better.
Also you might want to look at your antes and compare the percentage of the ante to the BB. I thought that some of them looked a little small compare to the amount of the BB, but without doing some calculations I can't say for certain.
About the breaks, I was thinking that if you went with 45 min levels you could take a 30 min break after 4 levels, that would be 3 hrs 30 per 4 levels, and after 8 levels you could take a dinner break of 1 hr instead of 30 min. That or go with 50 min levels and take a 10 min break after each similar to WSOP, and the dinner break after 8 hrs would be 1 hr long. That would keep everything even, but will add some time onto the length of the tourney.
Something else to consider is the type of players involved. IF they are mostly novices then this probably won't last as long as you think. If they are seasoned it will probably take longer than you think. But you probably already thought of this!
