When trying to move UTXOs around to get those 25 millions, I notice that suggested fee is in the hundreds! Is it a good suggestion, or could I manually try a lower fee? What are the lowest fees nodes will stake-mine by default?
Yes, this is an unexpected consequence of the repeated 4500 deposits - the transactions become very large.
I don't think the miners really care. In other words the 1 SMLY per Kb is the default set in the wallet for sending, but I don't think it gets checked by the (miners') SMLY wallets once the transaction has been set up and sent to the mempool.
By all means just try a lower fee and see what happens.
You should be able to do this in the command window using e.g.
settxfee 0.1
Maybe try a smaller transaction first