I have been using SeaFoam the last couple of years, with no problems at the spring start up. I can't see being off by 5% or so on the stabilization fluid to gas ration would matter a whole lot. What _might_ help would be to use some ethanol-free gas (if you can find it). Not sure what alcohol would do sitting in a tank for 3-4 months.
Nice find, that AGM battery. It might help to take it out of the bike, and put a battery tender like device on it.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.