The 513 is 8 more
No, it's 208 more..
Yes, but the 2nd 100 is reverse-wound, so it cancels out the first 100, making it an effective 8.
....except when they're not. The 305 is a 25 1/2" scale. The rest are hybrids, half way between a Strat(25 1/2") and a PRS(25").The 513, 305 & DC3 are all 25 1/4" scales so they are true Strat scaies