Searching for a lost dog - please advise

Our dog sitter moved 60 miles away from us. We were passing her new house on the way to our location, so we dropped the family dog off with her at her new house. We thought it was fine because our dog had stayed with her before. It was supposed to be for one night.

Turns out she's moved in with her boyfriend, who left the front door open literally 2 hours after we dropped our dog off. They lied to us about it and didn't tell us about it until the following day. Then they lied more about sightings of him. It's a long story but we ended up getting the coastguard out because of something the boyfriend said, and the coastguard basically told us the boyfriend had lied to us. We didn't realise the extent of the lies until 2 days later, and I cut him and the dog sitter out of the search because I can't trust a thing they say. Oh and when the dog originally got out, the boyfriend chased him over 2 motorways (flyover bridges) and a railway, onto a military firing range. The last trustworthy sighting we have of him is by staff on the firing range.

I have been off work unwell for over a year now. I am recovering and looking at part time jobs again, but I was bedridden at the worst of it (just before Christmas). The one overnight trip we were going on was a big deal for me. Now I'm driving 120 miles a day (almost 3 hours round trip, not including time spent searching) to try and find my dog in a rural town. My mother works full time, my brother also can't help much. My little sister is on summer holiday from uni so she can search, but she's basically doing what I tell her to do. She is sharing the driving which is really helpful. I am the one organising everything which is a lot of mental energy that I'm not sure I have, and I worry I'm going to crash after this.

I have postered the town, posted all over facebook in the surrounding areas, contacted local police, network rail and highways. I have contacted dog wardens for the county and two neighbouring counties. I have contacted kennels and vets in the town and the surrounding towns. I have gone door knocking in the town, posted leaflets through peoples doors. I am currently trying to thoroughly search the fields surrounding the firing range, because I don't think he'll have gone far. I have a few volunteers coming to help sometimes. One with a thermal drone, one with a normal drone and the other has sniffer dogs, so that's great. We've set up cameras in an area where we think he's been sleeping sometimes but we haven't seen anything for days.

I'm at a loss at what else to do, without making my health worse again. Any advice on what else I can do? Any advice on how to find volunteers in an area I'm unfamiliar with?