Actually, my previous answer isn't entirely correct. SubTotal. writes BT-50 (buyer street/house number) and BT-44 (buyer name).
BT-70 and BT-75 are no mandatory fields in the e-invoice specification and SubTotal currently don't write them. Where and how did you get those error-hints?
SubTotal does not support all e-invoice fields, only the most important (and mandatory) ones