I think you can mix any role and sometimes can be a good idea: BA and tester, PO and BA, PO and dev and so on, but most of the time this is a VERY BAD IDEA! From my point of view, any role should be a stand-alone role and you shouldn't mix them, because you'll lose the productivity of the person. It doesn't exist 50-50 % of the time. You'll have the context switching, you'll have sprints in which you'll need to behave more time as an SM, other sprints you'll need to be more of a tester and this way you'll completely destroy the velocity of the team. You might say scrum is not about velocity and prediction, but if you think that way...why would you actually use scrum and not XP? I took myself multiple roles in teams and it was nice, but in my opinion, if you want a good product, you should hire a dedicated person with experience in multiple agile frameworks and let the team decide which "way" they want to go. You can call that guy, scrum master, agile coach, agile master, it doesn't really matter.
Regarding the equal sign between SP and hours, that's a very bad practice in my mind. For me at least it never went good in the long term. Scrum is a development process, not a management one! A story point is a sum between uncertainty, time and complexity. For example with my experience, I would finish a story in 3 days, but you would finish it in 10 and your best friend in 7. We somehow will manage to get to the common ground but in the end, before starting the story I leave the team, or just get sick leave. At that moment the stakeholders will get upset because the team did not deliver what they promised: finish the feature in X days. "As a tester, you help define requirements", is another thing with which I do not agree. In scrum, you don't have testers and devs (see the pig and the chickens story), but let's ignore that for the moment, in my mind as a tester you need to check the quality of the product, test it not help the PO to do his job. The entire team can help him to do that, but if he really needs more in deep knowledge he needs a BA, not a tester!
Another thing is that the SM is not described as a “humble servant” anymore. This was a bad description and in the scrum guide 2020 it was changed and now the SM is described as “true leaders who serve the Scrum Team and the larger organization”
All in all, it's good that you got something that works for your team, but in my mind you can call it whatever, but not scrum. Besides the scrum ceremonies, I don't see what you really use from the framework...but again...if it works who cares how it's called, right?
