No Access To Apple ID Email - Can't Remember Password

Hey guys. My dad got a new phone and can't remember his Apple ID password. His parents passed away a couple of years ago and he has a lot of precious photos on his phone that he cannot go without. Anyways, his old phone has the photos. The apple ID on that phone is an old work email that he no longer has access to. To go along with that, he doesn't remember the password for the apple ID. I set up a brand new gmail account to use as his new apple ID on the new phone. Attempted to do verizon content transfer - it left out about 600 photos - all of which are important ones he needs/wants of his parents and other stuff. We then went the google photos route and the same thing is happening, for some reason the photos are not wanting to back up to google photos on the old phone. I use google photos and even matched his settings to mine - still no luck. We tried the airdop method but the old phone asks for the apple id password everytime. Same for trying to email. Any advice? Tips? Tricks?