1 - Whats is the limit for sendmany?
2 - Can i batch a large number of payments (several hundreds)?
3 - Does an error in processing any address would interrupt the whole process?
There is no hard limit on the size of the amounts objects you pass, but you may at some point reach the standardness limits on transaction weight.
As only one transaction will be created, an error processing any address will interrupt the whole process.
For the sake of the example here is a regtest transaction with 802 outputs (could not copy paste here as it reached the characters limit).
