I’m just going to keep saying how I want it said
Least he can have a choice when he’s older 😂😂
That's absolutely all that matters. You can't expect people to instinctively get it right the first time they meet him, but once you gently correct them, if they don't then pronounce it correctly (unless it's extremely complicated and they try hard, but just can't get it), it's the height of bad manners.
The name Isaac has exploded in popularity recently and I've also noticed a few babies called Issac. However much my instinct is to pronounce it 'ISS-ukh' and not 'EYE-zukh', as soon as the parents confirm that they intend it to be pronounced the same as Isaac, that's what any decent person does.
We once met an American who, although otherwise quite nice, was a bit of a know-it-all (KIA). For some reason, he saw fit to show off his ignorance regale us with a tale of when he met a man with the surname 'Ham' and that, when Mr Ham had introduced himself (pronouncing it like in standard English - I didn't care catch whether he was British or not), KIA rudely 'corrected' the man and insisted "NO! YOUR name is HAAAAARRM!!!" Considering that, even in many American accents, it would be pronounced with the same short 'a' sound, he just came across as really dim, arrogant and ghastly.
Even if Mr Ham had said that his surname was actually pronounced as 'Pork', 'Bacon' or 'Awopbopaloobopawopbamboom', it's his name, so how about you just accept and assume him to be the authority on it?!