If the Habs are trying really hard to move Weber's contract, I doubt they would have interest in taking on Dadonov. Our cap situation isn't great. I guess they could take Dadonov for a 2nd, then retain 50% and trade him for a late pick in the summer but I think that's unlikely.
On an unrelated note, I really don't know what they will do with Petry and what his value is. I find it hard to believe he has negative value, but I also don't think he has much value at this point. We might get a mid round pick to unload that cap hit without retention, but might be able to get a good prospect/pick if we retain a fair bit. That being said, we might not have enough retention slots for other moves, and retaining a contract for 3 years is never a smart decision.