Just to confirm – no “Ken” in glasgow, Ayrshire or east side. I’d also say all your “romantic” broons style Scots doesn’t sound genuine – it sounds like an Englishman pretending to be Scots without understanding the subtleties. May only offend the Scots (and maybe only half of them) but people like books about places they know…
I also don’t think your character in the first quote says he’s sorry about his friends dad. Glaswegian men do not express emotions to other Glaswegian men, except about the fitba. He may say something like “that was shit what happened tae yir da” but he won’t be sorry. They also don’t “fancy” going to do anything (other than burds) – “ye wanna go find some mushies” might be appropriate; although I’d say it’s not the normal drug of choice in Glasgow, and I don’t think they’d describe it by the act of foraging the crop rather than the destination – “i wannae go get some mushies an get aff ma face, ya comin?”
When is it set? Polis would be normal for anyone who hasn’t grown up in the YouTube era (so probably born late 90s onwards) after that you’ll hear feds etc creeping in – but polis wouldn’t be out of place.
For your sas comment I’d go with something like “whit the **** are you wearing, we cannae go like that, we’ll stan oot like the Pope at Ibrox”