It is hard to give an opinion on a video if that is too much clearance, but it looks normal to me?
Guides that are too tight can, and will cause an issue, but they need to be very loose to pass oil with those seals.
I do not see how excessive oil would pass those seals with that little movement.
Do you have a bore scope to see the oil and carbon build up inside the combustion chamber?
I cannot count the number of turbo Buick heads I have removed and never have seen "excessive" carbon build up not matter how screwed up engine runs.
Maybe you should keep looking for your starting issues elsewhere?