Before I made the original post I tried with the top C and the tab broke. Luckily the spring and the front key stop hold the key firmly.
A few minutes ago (before I saw your post) I tried again and then managed to get one key out. The rest then had more space to wiggle and came out more easily (with no more broken tabs ).
The screwdriver just got in the shot I used a smaller/flater one.
Also some of the weights have micro cracks (a few white keys, black keys have a different design so they can't crack as easily).
Thanks for the reply, here are a few more pics.