Can a block have multiple coinbase transactions? Also is there a limit to the number of signatures a multi-sig transaction has or requires?
A block can only have one coinbase transaction. You could however send the reward+fees of the coinbase transaction to multiple addresses (of any type) just like any other transaction. 


  is there a limit to the number of signatures that a multi-sig wallet can require?  


https://bitcoin.stackexchange.com/a/28092/87716