All the building supplies in town have had super extended lead times because of plant shutdowns/general COVID constraints.

So offer to extend the contract as long as it is necessary for the seller to make good on their end of the bargain, or for the fee of your costs  be willing to terminate the contract. 

It reopened May 15th and I haven’t had a vacancy and it extends into November.

@Soniel Estime a business partnership is about as risky to a friendship as extended travel.

I’m unsure if he’ll extend the lease.

Couldn't I get a high powered booster, then buy a hotspot, buy an unlimited $70/month plan for the hotspot, and perhaps get a wifi-extender if the hotspot isn't big enough to cover the house?

Time scales are extended (in my experience) and sometimes products are simply not available.

If talking to family (assuming this is extended family/friends and not your nuclear family) is what is shaking your confidence, then I would not continue to engage in that behavior.

I'd start getting addendums over to the seller extending escrow if that is the route you choose to go down, and learn the process for wherever you are so you can better estimate what to do with your current residence (probably take it off the market temporarily).

I think his tenants are people that want to live off base that usually lives in a nearby extended stay type of residence.