Was Bach the first to use thumbs on a keyboard?

So no, Bach was not the first composer to use the thumb. As the harpsichord transitioned to the fortepiano (certainly during CPE Bach's lifetime), avoiding the thumb became less important in good technique and CPE might have boasted about his father being in the vanguard of Classical technique.

1. What kind of keyboard did Bach use?
2. Can you play piano without thumbs?

What kind of keyboard did Bach use?

JS Bach was open to use many different forms of keyboards and he equally enjoyed playing the organ, harpsichord, clavichord, Lauten-Clavicymbel ("Lute-keyboard", e.g. used for BWV 998), whatever was available and suitable.

Can you play piano without thumbs?

You can play! While the thumb is used for connecting a line or phrase, it is still possible to use good pedal work to connect the lines.