That sounds correct for the chain, if you have a chain in good condition then try it on the bar, see how the drive links fit.
As far as oil mix goes, no not necessary with the newer two stroke oils dedicated to air cooled engines, in my own vintage saws I have run 40:1 mix since the 70`s with no issues at all. I have had many of them apart for extensive cleanup and ring replacement, pistons and crank bearings are always nicely coated with oil. This ole saw has been running on 40:1 since 77 and always starts up with a couple pulls.