1. Yes. "Slingshot fire", it's still fire. It's not on the same level as fire attacks from the Mera Mera no Mi, sure, but Kuma's paws still deflected it. Showing that his deflection powers nullified the effects the fire would have had on his paws, i.e., burning. This is further supported by the fact that Zoro's flying slash made direct contact with his paws, and was repelled without cutting him. Again, the attack's effects were nullified. Therefore, the same would happen with attacks from Sabo, and Kuma can repel Sabo while he's in his fire form since he repelled fire itself already, as well as the immaterial flying slash and the non-tangible air itself. There's no reason to think Kuma can't repel Sabo or any attacks from the Mera.
2. @Bold How can you already be getting desperate