To 1: Heres a thought about bitcoin not really having a major stablecoin on its protocol:

I know tether got started on bitcoin's Omni. Also, i heard of the HRF issuing a bounty to make a USD peg. But, imagine if bitcoin had as much stablecoin activity on it as ETH. What would happen if there was a fork splitting bitcoin? Everyone who holds 1 btc would get 1 of the new version too. But would everone holding 1 "bit-usd" get a second version of that? The stablecoin issuer would only be able to honor one version of the "bit-usd." Therefore the stablecoin issuer, if holding a large enough amount of user value would have to make a decision that would have way too much impact on which chain gets chosen. Even if it's not in bitcoin's bests interests.