Hohner A D help with broken thumb strap, a lesson book, names of buttons, and shoulder strap!

[Musically Inclined]

Good morning,
I was playing my Dad's (85+ year old accordion) last night and the leather thumb strap tore in half.

Does anyone know how to take out the "rivets/screws" so I can get a replacement strap and reattach it? (see picture)
Does anyone know the names of the buttons so I can teach myself how to play this squeezebox?
Does anyone know where to buy a lesson book for this model? (Since I normally play the piano accordion, etc)
Does anyone know where to buy and how to attach a shoulder strap?

THANKS FOR any/all advice. I am grateful to be in this forum.
Christine

 

[Glug]

Last time I needed to replace a bass strap I found a cheap leather belt on Amazon that looked the right size and cut a piece out.

I've also discovered Chicago Screws which are available in many sizes

Amazon.co.uk : chicago screws