You need to get viral meningitis/encephalitis ruled OUT. This will require a spinal tap. Viral meningitis is different than bacterial meningitis, bacterial causes and extreme high fever and is usually rapidly fatal.
I have had viral meningitis that progressed to encephalitis. It started with an extreme headache, no other symptoms. A transient low fever like your younger son had is common.
Head pain this severe requires pain relief treatment. I have had headaches so bad they have caused me to go into shock, which can be deadly in and of itself.
This is encephalitis time of year. There are quite a few different viruses that cause it and all are transmitted by mosquitoes. It is a disease that is reportable to the CDC.
Also, they could have West Nile, another of the mosquito born viral diseases, which manifests from no symptoms to deadly and everything in between.
I think you need to find a way to get the hour to the better hospital. Either via friend, neighbor, paramedic...something. If nothing else, call the emergency department at the good hospital and ask to speak to the triage nurse. They will tell you whether or not you should come in. Make sure to explain what the other hospital said.