The pump takes a bit of getting used to and that includes getting the doses correct.
As you say, it is usual to need less insulin with a pump and that is certainly something I found. My total basal went down from 20 until per day to 15 (which just happens to be the 75% you mention)
And my insulin to carb ration reduced significantly too.
Once you start on the insulin, you will probably do more testing than usual at the start and, if your doses are out, you can adjust them.
It is better to be conservative at first: too many hypos and you may feel like yanking your Omnipod off and throwing across the room (or is that just me?).