3) Sidechains + Lightning Network
This is the path of scaling the Core team choose. And I think it's a very elegant, decentralized approach to scaling.
Both are already failures - if you're realistic about it. I don't see any connection between the bad ideas of Gregory Maxwell and a few others, and Bitcoin as a system. Sidechains are one of the dumbest ideas I've seen in Bitcoin ever. The ideas was proposed 3 years ago, whitepaper written 2 years ago, and there is no functioning system and I predict there will never be. Lightning is quite interesting, but will be a failure, too. I will be on my beliefs by selling Bitcoin for a better alternative when it arrives. There are deep economic reasons for these ideas to be bad, but you can't expect from core developers any understanding of it. They don't even see the incentive and scaling problems as they are. "Scaling Bitcoin" is a misnomer to begin with.
7) Corruptible devs
Also the bitcoin developers are decentralized, even if the Core team has control over the github depository, everyone can host bitcoin's source code on his server and work on the code.
No. Bitcoin dev is centralised around a small group of people, for good and bad reasons. Nobody can add just add any patch to the system. Forking blockstream/core is basically starting a new chain and project.