Alternatively, if you aren't in a hurry, wait until the mempool empties and then consolidate at 1 sat/vbyte.
Could be waiting quite a long time for that to happen again... The mempool hasn't been close to empty for quite a while now 
https://mempool.space/graphs#1m
I don';t think it will take that long. In the graphic you posted the mempool was cleared at 30/01.
And there were other moments last week (07/02) when a 3 sat/byte would also get a confirmation as well.
Personally, I would just fire a 1 sat/byte transaction with all those 40 inputs and wait.
It is probably going to take at least 1 week to get a confirmation. By the end of the month he will very likely to have all inputs in a single UTXO for a very low fee...
Using this tool, 40 inputs and 1 output would have about 6000 to 2700 bytes (depending on address format) and a 1 sat/byte transaction would range from 0.00002794 to 0.00006 BTC to transact (depending on format)
I would certainly make a 1sat/byte tx.