1) Justifying your offer:
If you have to justify the validity of your offer, it probably won't be accepted. Hell, you have 5-6 guys telling you it isn't a good enough deal and yet you're still trying to convince us how it makes sense. This isn't a judgement on you, but rather a judgement on whether or not we think you're offering enough.
2) Assuming what the other GM needs/should do:
Nobody wants to be told how they should run their team. In my experience, there's no better way to alienate a rival GM then telling them/trying to convince them that they need to rebuild. Expecially if, as you mention, his actions are showing you he has no interest in rebuilding. You need to meet the other GM on their level, not convince them of yours.
Keep in mind I offered Getzlaf/Doughty/Schneider/B. Smith which would help him greatly on D and in goal (he had Luongo), while hurting him a notch or two on forward, and the owner balked, because he knew he wanted another stud in return.
Honestly, I don't see you have the star power to acquire Ovechkin unless you coupled Sedin with Rinne, and thats too much to give up. Since you're already offering two of your best players in the deal, try telling him to pick any 5 skaters from your roster and chose 3 of them to offer straight up for Ovechkin. You'll be giving up alot of production value, but Ovechkin's trade value means that one year from now if he doesn't work out you could still probably move him for a package of equal or better value than the one you gave up for him.