Phew, I read the whole thread - rope or cable is a more applicable term. Think big, arm-sized battleship mooring cable. You seem to have reached all your goals and ended up with a cheap limited range vehicle. Power use at 'cruise speed' seems to be around 5-7 kW in favourable conditions?
Have you considered getting one of those
diesel generators which can be had for less than $1000 - at least here in Sweden, cheaper still directly from China if you buy 5 or more.
You'd only need a smallish one, 5KVA should suffice to keep you on the road. The small 1 cylinder diesel engines used in these machines are relatively simple and can run on more than just liquified dinosaurs, SVO or filtered WVO usually works just as well.
You could make it removable so you'd only need to drop it in when you plan a trip which exceeds battery range - eg. a trip to one of those EV jamborees. You'd need to make an extension for the exhaust to keep yourself from suffocating and you might want to wear ear muffs to survive the racket those things make - but it could also be placed on a trailer of course, even though that would decrease the efficiency of the combination. If you really want to make it fancy you could make it autostart when the batteries get below a certain threshold. Fuel consumption for a 5KVA machine would be around 0.8-1 l/hour full load.
With one of these you'd be able to turn your limited range all-electric into an unlimited range diesel-electric series hybrid. A locomotive, sort of... But with the advantage that the oily bits can be taken out at will to return to the all-electric configuration.