Sorry to hear that PT. Hope your daughter and any other passengers are all OK!
1st) The 5W20 can be added to your oil changes 1 or 2 qts at a time. I use 2 qts of 5W20 with 3 qts of 5W30 in my wifes RX-300(which calls for 5W30) for the winter time. No issues.
2nd) Many Honda, Nissan and Subaru vehicles use the same part #'s for oil filters. So if she plans on purchacing another one of these vehicles, your good to go. Even if it's a Honda filter from the dealer. No issues.
3rd) With the Z-1, well, you'll be OK if she purchaces another Honda. Might be able to use it as a Top OFF fluid in other applications. I've used Honda Z-1 and Toyota T-IV in DexIII/Merc applications(GM vehicle) when I've had orphans. No issues.
4th) No, I don't know what duel pump fluid is. Is it for the P/S ? If it is P/S fluid, it can be used in vehicles that use P/S fluid and not ATF for their P/S. I use Honda P/S fluid in a GM P/S unit. Have for 20 years. No issues.