There is nothing we can do about this transaction unless if the network congestion drops a lot or if you can contact the company who sent it and ask to make a double-spend or to rebuild this transaction with a higher fee.
I think your first suggestion will be the best, he will need to wait till the mempool has been decongested in a way it will be able to accept 2 sat/vbyte transactions. But very possible for ViaBTC node to still pickup the transaction again, but I am thinking the fee may be as high as that of Poolin as a result of high inputs (although, I am not sure). The transaction can not be double-spent because it does not support replace-by-fee. Only what the sender can do is to use CPFP, but the change address UTXO only have 0.00046802 BTC which can not make both the child and parent transactions to be confirmed, unless more bitcoin can be spent from the sender's wallet another address in addition to the change address UTXO in a way high fee will be included that will get both transactions (child and parent) confirmed. I have not used Bitgo before, but I have not seen a custodial trading platform that their transaction fee will be as low as that.
Lately even I guess I have seen it today too that the fees were below 7 sat/vB. So considering the last few weeks when the fees were crazy high like over 200 sat/vB, if the sender company can just rebroadcast it with at least 10 sat/vB then I don't think OP will need to wait much longer time.
Yes, you are right. I have heard before that if a sender do not open his wallet and not able to sychronize with the blockchain, this can make the transaction to leave almost all the mempool (although few mempools may still have it) with the wallet not able to rebrocaste the transaction automatically as it is not synchronizing with the blockchain, then the sender can be able to be rebrocasted it manually after leaving almost all the mempools, but I think this may differ from one wallet to another, I have once had a frustrating stuck transaction for over 2 months before it was confirmed, I have my wallet not synchronized for over 30 days to the extent I was not able to see the transaction on some mempool again, but nothing was reflecting on my balance. I had to wait until the transaction was confirmed. The sender may not be able to rebrocaste the inputs even if he has full control over the wallet.