Been together 3 years. In the early days he used to waffle on about his ex 24/7. Now he barely mentions her but I've noticed that a) he has photos of her still on his pc, b) he constantly whines about the virtues of marriage and c) tonight he were watching Harry Enfield, Wayne and waynetta where she tells him to sling his hook and DP says. " I always found this episode quite sad actually". Yeah because it reminds him 100% of his ex and their break up. He's now got drunk and is being his usual arsehole stroppy self with me. AIBU to assume he'll never get over his ex?
The three examples you've given do seem to be you maybe reading things into stuff he's saying, especially Wayne and Waynetta. Even if he didn't say it because he was missing his ex but because it still reminds him of his break up, it's OK for him to still be sad about how he felt at that time without being disloyal to you.
YANBU to think about giving up on him if he's someone who's a stroppy arse when he drinks too much though.
What's he like day to day?
Could you be overthinking him still pining after his ex? It does seem unusual for it to be a problem for you three years on. Are there other things that make you think he's comparing you etc?