Dear Vicky:
I see that I only addressed part of your request.
Aplysiidae and Ellobiidae are both heterobranchs, so they go last. Aplysiidae is Opisthobranchia whereas Ellobiidae is Pulmonata, so Ellobiidae is after Aplysiidae.
Flanking might be
Saccoglossa (e.g., Juliidae)
Aplysiidae
Nudibranchia
Ellobiidae
Styellommatophora (e.g., slugs)
Zebinidae and Vermetidae, which go before heterobranchs, are both littorinimorph caenogastropods, so no help there, and it becomes a matter of opinion and the latest ruminations of the various experts. My preference (and that's all it is) is to put Zebinidae "earlier" than Vermetidae (which might be near Xenophoridae).
Hope this helps.
Bob