Aldo, I agree with Bob - they have supplied two fill points in case one was inaccessible after the engine was installed. I haven't seen one like that before. It is just part of the timing cover, not the crankcase, so it was probably a production option. You are supposed to fill with 600 ml of oil, which brings it right up to the top of the thread, but I have found that some engines leak oil during storage between uses if I do that, so I fill to the bottom of the thread.
That is a Choke-A-Matic choke - not one of my favourite mechanisms. You can adjust it so that the choke is fully open at one end of the range and fully closed at the other, but the link is springy so it may not work well. You might try oiling the choke pull-out and see if you can work out some of the friction. From your symptoms I suspect that at some point, someone has adjusted the mixture to compensate for the choke not opening completely, so if you open the choke properly it may be lean. That would explain the warm restart issues.
The governor spring seems to be a goner. You need to do something about that.
I won't get into the family issues question - for me family ranks ahead of accumulating even more junk that I don't need, but everyone is different.
