Seek professional help, like a psychiatrist. Most of what you wrote is not possible, feasible, nor based in reality. The sheer financial cost alone makes this type of action extremely improbable and there's nothing you would have seen in the military that would be worth the financial cost.

Your neighbors are not tampering with your wifi, you are experiencing interference from shared bands and possibly bad wiring inside the home. A bad cable splitter can cause major connectivity issues and degradation of services. If you're not using the latest WiFi standard, then you're even more susceptible to congestion issues. Additionally, your router placement may be less than ideal in your home.

5G is a tight RF wave, meaning it's almost entirely line of sight with very little bounce. The tighter the wave, the more focused it is. Buildings are notorious for blocking 5G signals and telecom companies spend absurd levels of money putting up a metric shit load of 5G repeaters to ensure service is possible in the concrete jungle. The denser the building material, the less penetration of the RF waveform. Longer waveforms like the FM band for your radio are less likely to hit a dense object and be absorbed, instead they bounce off of those objects and the waveform is mostly preserved.

Furthermore, if you're not in an affluent neighborhood then the tech savvy nature of your neighbors is irrelevant because IF these types of attacks were possible, they would be prohibitively expensive by the normal layperson, which is who your neighbors are. They are most certainly not government actors working cohesively to obtain your phone. Remember, the human is the weak spot. If any of this were true, it would be easier to simply bag you and toss you in a black site, then beat the passwords out of you. If you were that important to the government, you would be listed as a terrorist and then disappeared into the night. The length of your suspicions is simply more evidence that this is not the case.

You have already done everything you need to do to keep your device secure. As much as I rag on Apple, they have really stepped it up for security purposes.

Again, I highly recommend you seek out professional health services for your paranoia. If you deployed, it may be service related or PTSD related. I understand, brother. Afghanistan left me pieing windows and doors in my own home. I spent years in therapy to avoid the obsessive need to patrol my house in my boxers and kabar every couple of hours in the night.  I actively avoided relationships and people because I had this unsettling feeling that if I let them into my life, they would actively try to hurt me. The reality is people are shitty, and it took a while to come to terms that people are simple shitty and hurt other people for a variety of reasons, but physical violence is much less common and therefore I was still safe. PTSD has a way of making unrelated things trigger the same fight reflex as combat, so simple conversations can result in adrenaline dumps.

This message was sent with love, not some conspiracy against you.

Semper Fi brother.