I have this probem with my dad

I have this problem with my dad. To fully understand you need to hear it from the beginning. I love my dad unconditionally, always did, but I'm having a hard time getting through to him. A couple of years ago he had a stroke. He litterally couldn't speak, hardly at all, for like three weeks. My dad has never been much of a talkative person, but now it was like I met him for the first time and had to get to know him all over again. His mind was perfectly fine and he knew exactly what to say, but when he tried to talk the words just wouldn't come out right. He would sound annoyed and angry even though he wasn't. He knew this, but because of it he couldn't explain what he really meant without sounding wrong. All this crashed down my mum and us. Now it has been 4-5 years since the stroke. It's way better now, but sometimes it still feels like he's a complete stranger to me. My mum and dad don't fight a lot and I know they love eachother but it also feels like some things get left unsaid. A while ago I probably had the most honest and open conversation with him. It was after dinner, we argued and the whole thing ended with dad leaving the table 'cause he couldn't say the things he wanted to say. It's not like he's handicapped or anything, but I hope you know what I mean. It's hard to explain if you're not there. Anyway, when I was just about to go to bed dad came down and said he wanted to talk. He was talking very slow and quiet, I could tell he wanted this to come out right without sounding wrong. He told me that me, my sisters and mum were the best thing that ever happened to him, that he was so scared of losing us. At the day of his stroke he was so damn scared. He also said that he never meant to hurt us, it was just his way of dealing with it without thinking first. He started crying and told me he would do whatever he could to make us a happy family again.

What can I do? I have no idea what to say to him. It's better now than before, but I know he still struggles.

Help me, please!