Not knowing the exact issues with the data, I can give you the general notion of how it works now (neither a perfect solution nor a generalizable one):
quantity field is basically all that you need. Say, you have an ingredient, its dosage and quantity:
aspirin 325 mg 1 tab per day.
The proper way is to map it to RxNorm concept 19082433 Aspirin 325 MG and put 1 in quantity (as for solid drugs quantity represents the number of pills/capsules etc).
Second example:
heparin 0.25 units per ml, 3 ml
Then, again, you map to 43011613 heparin sodium, porcine 0.25 UNT/ML and put 3 in quantity (as for liquid drugs you store the number of milliliters or another measure of volume).
For infusion rates we had a couple of pretty intense discussions and seems like folks ended up using the approaches that fitted their workflows and needs. My suggestion was to put the rate into the quantity field and the unit (mg/hour or something) into the dose_unit_source_value. You may also refer to this post: How to record an inpatient drug infusion?.
Does it make sense?