What I can gather from reading reports (and I’m no more expert than you) the old are certainly dying faster, but the mean for critical cases in Lombardy was about 65 yrs old. It could be lower now.
Younger people are hanging on better /longer in ICU conditions, but if that capacity is breached Then age will be much less of a factor in survival.
The issue of co-morbidities is also overdone imo, obesity counts and applies to 28-30% of entire UK population! Smoking clearly doesn’t help, but I don’t think it’s as deterministic as ‘old smokers are screwed, younger people mainly okay’. Seems much more like Russian roulette than that.