Sorry you need to be here.

There are a couple of red flags here
Infrequent sex redflag
Heavy smartphone use redflag
"I love you like a brother" redflag

I would suggest you put on your detective hat and start snooping. Taken together these items suggest the likelihood of an affair.

Can you check the call /text history on the phone? Can you check the phone bills?

Me 58: FWH (NC 32 yr), W 60, married 36 yr, DD 32