I'm on the other side of this too, like TheGoodEnoughWife.
Like the cooking example you mention. I feel like I don't understand why he feels the need to mention it IYSWIM?
hints/tips to be able to deal with this
I don't know if I have any hints/tips but I do have some insight on why he might feel the need to mention his wife's cookery skills when you're cooking, or whatever.
Have you met his daughter yet? I say this because I've realised I was purposely mentioning DH more than usual to triple check my boyfriends reaction in the week or two before introducing him to my kids. I wasn't consciously doing so, it was more of an instinctive thing. And I think I was right to do this - my kids' first question when they were due to meet him was 'Is it okay to talk about Daddy in front of him?' I was able to assure them that not just in front of him, but to him. That he's interested in hearing about Daddy.
And that's another reason why I find myself opening up and talking about DH more even than I do usually, to my boyfriend. Because he and I are still getting to know each other, and marriage is a really important part of who I am. And he knows and appreciates that.
Another observation. I apologised one afternoon for having talked about my DH rather a lot. My boyfriend said he found it a compliment, pointing out that I discuss DH the most when I'm feeling happy. I'd never realised that before! Now I'm earlier on than your BF in dealing with the grief (18 months), and this might be a highly individual thing. But I suspect not. Before I met my boyfriend, I spent a lot of time thinking about the terrible times of when DH was diagnosed, undergoing treatment, visiting him in hospital, his funeral. (I made an effort to talk to my kids about the happy times, but it was an effort, not something that came naturally.) Now that I'm in love all over again, happy moments in my marriage, and things about DH before his long illness, spring into my mind all the time.
Now, about feeling insecure that this isn't a relationship he chose to end.
I understand that feeling. If she hadn't died, he wouldn't be available to be with you now. That is a bit of a headfuck.
Ultimately you need to work out if it's something you can make your peace with or not. I don't think everyone would be able to, and I don't think that means anything bad about an individual if they can't.
As I met my boyfriend through work, I've had vague guilt about what would have happened when I'd started working with him if my DH hadn't got ill and died beforehand. Our attraction to each other was so strong from the instant we met, and our personalities clicked so naturally - I would never have cheated on my DH who I was deeply in love with, but... would I?
Then, very recently, my boyfriend and I realised that we met 4 years ago, when we were both in our previous relationships!! We attended the same industry conference and were in the same break out group of 12 people - we don't remember noticing each other at all!
Who we are now - partly as a result of the shit that he was going through then and that I've been through since, is part of what makes us right for each other right now.
Widows and widowers get told a lot that there's no right way to date again after losing a spouse. You have to find what works for you, and your new partner, and crucially your kids. So if the balance at the moment isn't the right one for you, the only thing to do about that is to discuss it with him.