On your point 5., It would probably be more accurate to say we know groovy is going away eventually, and no official timeline has been given for when that will be.
Historically, smartthings has sometimes removed features with only a few days’ notice. It seems unlikely they would do that for the groovy cloud, but there’s no guarantee.
This is one of the reasons that a competing (tiny) company founded by former smartthings users has developed a hub which runs entirely locally except for third-party integrations. It would continue to run both smartthings smartapps and their own automations even if both companies went out of business.
There are some community members now who have added it as a secondary to their smartthings systems to provide local operation and back up. It is available with a UK frequency Z wave stick, and I know a couple of people in England are using it.
It’s a very new product and needs to be considered as basically an ongoing beta. And it’s designed more for people who want preset automations, for example, there is as yet no mobile app. It also requires a high degree of technical skill at the present time. But it’s certainly worth looking at if a long-term horizon for groovy smartapps is a requirement for you.
https://community.smartthings.com/t/hubitat-elevation-hub-home-automation-that-is-local/117107