>How many times has bitcoin hard-forked because of the protocol being compromised?

Looks like there were some. https://news.ycombinator.com/item?id=15907735

>How much daily volume is it currently supporting?

Doesn't matter. Any other coin can support the same daily volume (and many others usually do)

>How does the velocity of the codebase compare to other coins?

Terrible. Constant in-fighting. This is what is hurting bitcoin right now.

Edit: added hard forks link.