Foundation is not a stage u should joke with nevertheless all design must be optimized. Assumption base on layout without dimension
Factors to check out for. what depth is your foundation
Size of block ,
Soil pressure: This should be taken serious because it can take out your foundation when the area filled is so much and no other forces acting behind your foundation .
Dpc: Your dpc slab will make your foundation a load bearing wall except you are introduction a beam to take care of that reason you need fill your foundation block wall with weak concrete and your foundation strip with grade 25 ..
I reject a job from a nairalander I don’t know self when he said the cement I quote is much and blocks , I requests he get everything and have someone on site as well. reason he said someone quote lesser( The scope of work is different) .I build and sleep not using weak concrete to cut cost and ve jobs
I’m in transit can’t review much or advise more ..