Aremke my friend, you know how well I enjoy your fan story. You also know how particular I am when it comes to fanfictions and fan works. Regarding our discussions elsewhere on the net, you are well aware that I would be one to help you in any way that I can.
What I can tell you right now is that email you got is indeed fluff and no credible substance. You have the dates from the timeline and the info from the bio from the Daizenshuu guide thanks to Dayspring. I am looking forward to your next storyline in your Yamcha Elsewhere fan manga. If you want to ask any questions of me, just catch me on AIM again sometime or here, or our other usual net haunt.
As of right now, you are still right on track. The only thing I'd be careful of is having Yamcha know Kaioken. I think only Goku was taught that because his Saiyan body structure could endure it. Only then because King Kai himself developed it, but even he could not master its use. I think seeing Goku's saiyan strength and ability to jump so high in ten times gravity spurred him to see if someone could master the technique. I don't actually think anyone else was taught that technique. If they were, it was only the basic Kaioken that King Kai is seen to use (catch me on AIM to see a clip I made of this rare scene) and not any of the multiplied ones that Goku became a master of.