He sounds lonely and "clingy"...but nothing of what you wrote gave me any concern that he is being anything more than extremely overly friendly and lonely and clingy. Seems like he doesn't know how to make new friends at his age or around his age..and without his wife anymore he is most likely still hurting and feeling alone. Grief as you get older can take a long time to pass.. How you want to handle this is up to you--but to me what you described doesn't sound threatening or as any 'danger' behavior. Creepy people really cannot help but escalate their creepyness fast..but he doesn't sound like a creep to me. If he was he would show up, text you relentlessly, phone you relentlessly - but everything he seems to have done is respectful to try and make himself available should you wish to accept him as a honest friend.