Just started some last minute planning to Newfoundland. Will have 2 wks to spend and will start in S

Just started some last minute planning to Newfoundland. Will have 2 wks to spend and will start in St John's. Will also head north to the Trinity/Bonavista area, Gross Morne and will ultimately fly out of Deer Lake. I'm having a hard time finding companies (I know it will be expensive due to drop off fees) that allow for the one way rental. Has anyone done this recently and if so, can you suggest something. Hertz doesn't have anything in Deer Lake, Enterprise online air ticket sales doesn't allow for one way; Budget only has smaller cars (need something big) and Avis has limited options. Just thought there might be something out there I'm missing. Also, has anyone stayed in St. Johns at either the Ryan Mansion Hotel, Leaside Manor Heritage Inn, or the Park House Inn?? Recommendations would be welcome. Can anyone tell me what to expect (absent hurricanes) for weather conditions from mid August into early September? Thanks
online air ticket sales I can't help with car rental--I'm online air ticket sales afraid rental companies here have it very much their own way--although I seem to remember Thrifty having a desk in Deer Lake, but that was several years ago, so maybe not now.
Usually September is pleasant here, with daytime temps between 15-20 and frequent online air ticket sales sunshine, plus no blackflies. I gather you heard of Hurricane Igor in 2010. It was quite destructive of roads and property, although only one life was lost. However, I've lived here almost 50 years, and that was the only full-blown hurrican I've seen here.
Take a look at Maxxim Vacations and see if they have anything that suits. We did a fly/drive with them some years ago, arrive St. John's, depart Deer Lake, and enjoyed it very much. Although the accommodation was arranged in advance, we were free to spend the days as we chose. We often met other Maxxim travellers at the BnBs, so could exchange stores, and in the case of those travelling in the reverse direction, learn what lay ahead. Overall, it was a nice compromise between the freedom of travelling on our own and the comraderie and convenience of a small group.