PG, yes, ask around, get a second opinion.
Do be aware of hidden sugars, glocose, fructose, dextrose, maltose are all forms of sugar.
Fruit has natural sugar in, flavoured crisps, baked beans, alot of cereals, tom sauce etc etc.
Go for sugar FREE, not NO ADDED sugar, IMO that means they can't get anymore in.
The teeth you mention are very pitted, so food will get stuck in them, make sure he has a good brush after meals, after breakfast, not before. last thing at night, with only water to follow. Try & avoid stciky stuff, opt for chocolate over sweets & pref a bar, not smarties, as these tend to last ages. I was going to buy DD Winnie the Pooh choc buscuits, only to find they had £ different types of sugar in them!
Sorry, I do know this is obvious, just trying to help.
20 minutes after each mouthfull of food the teeth are subject to a bacterial attack, so if he has a tube/bag of sweets his teeth will be under attack for alot longer.