Well it sounds like he isnt cancelling the DSL, so if it doesnt work out he is just back where it was, configure the DSL as backup.
I do sympathise with Weaver, he is paying a ton for multiple business lines with higher priority faults as well, so he is paying a fair whack for his service.
Also 5G has problems that 4G doesnt have, I deliberately disable 5G on my phone.
There is people who use 4G as their day to day broadband, and every time I have used it, it doesnt drop out, has been reliable, so its worth him trying.
On your connectivity going down on firewall restarts, if you using pfSense 2.6.0 enable the PF counters patch, a new feature causes massive latency spikes on every firewall reload, the patch disables the feature. To be absolutely clear I have never had a 4g disconnect when hooked up to pfSense. Its actually DSL isp's that give me uptime headaches.