Rather than start with T250 stacks and 1/2 blinds (125bb) with a big early blind jump, I'd recommend a T400 starting stack (15/12/9/1) with opening 2/4 blinds (100bb) and using less aggressive blind increases.
For 8 players plus color-ups and re-buys, you will need the following chips from your set:
120 x T1
96 x T5
97 x T25 (includes 5x for T1 color-up)
40 x T100 (includes 5x for T5 color-up)
You won't need the $50 or $500 chips.
Set aside 20 x T25 chips and 15 x T100 chips for up to five T400 re-buys (using 4/3 stacks). Any subsequent re-buys (very unlikely) can simply use 4 x T100 each (12 chips total).
Your proposed stacks and blind structure above will likely end by L11 (50/100), or roughly 4 hours including breaks.
The following structure will also last roughly 4 hours using T400 stacks and 20-minute blind levels, but flows much better with no large blind increases:
L1 2 4
L2 3 6
L3 4 8
L4 6 12
L5 8 16
remove T1 chips
L6 10 20
L7 15 30
L8 20 40
L9 30 60
L10 40 80
remove T5 chips
L11 50 100
L12 75 150 **eot
L13 100 200
L14 150 300
L15 200 400