Sorry to hear that! While my dad is still with us, I’ve often sat and wondered what I’ll say at his funeral. Like you say how do you sum up a life in a few minutes?
I know my old man wouldn’t want anything mushy. He would hate anyone to reference him as a “hero” or anything like that. I think he’d love to hear the anecdotes because he always enjoys a good story so I’d be adding a few of them in especially the ones that paint a picture of the person he was and what he means to me.
Ultimately though you may have to accept that as wonderful as the English language is, it may not be able to describe every emotion you are feeling and the kind of relationship that can only develop over that period of time. The greatest writers of all time have been trying to achieve that for centuries and have only scratched the surface. Some things will always go unsaid but it doesn’t make them any less real.
I'm intending to focus on his qualities and what that meant to the family and those he impacted. It's easy to have good things to say about my dad as be was a good person. I think I'll write something that says what it needs to, simple and respectful.