My friend went through something similar with his Dad a few years ago. His Dad just needed some time to get his head straight. Got back in touch a few weeks later. He lived in Peacehaven too.
A couple of ideas for you, although I wasn't sure if I should even mention these because they might cause more stress, but I'll leave that decision up to you:
- If you think he might be checking his email but you don't have access to his account, an alternative to sending a read receipt email is to send one with a unique image and link url in it that no one else will visit. If the web servers logs shows someone visiting that page then there's a good chance it was him (especially if there was some delay since his mail host may immediately scan url's contained in emails). If you decide you want to do this and need help, let me know and I'll get a url for you I can monitor.
- If you want every oap in Peacehaven looking out for him, pop into the co-op in the Meridian Centre and put a notice up on their board.
I'm sure he'll speak to you soon. All the best.