Does the number of confirmations keep increasing until eternity or is there any certain max? I've seen transactions from years ago have 30K confirmations. But what is the record actually?
AFAIK the number of confirmations is just how many blocks are ahead of the transaction.
For example, if the tx was included on block 50000, if we finally mine block 51000, it will have 1000 confirmations. So, someone would need to reorg the 1000 blocks to "undo" the transaction.