How to set a DKIM record for a domain hosted within Route 53 when the mail server is not in AWS

I have a domain that is managed in Route 53, but the servers are somewhere else.

My emails from that domain are being rejected for not having SPF and DKIM. I was able to set SPF within Route 53, but not DKIM. The key i brought from the mail server hosting is being rejected for being too long (as a TXT record) and it is not clear or evident solution is being offered by Route 53.

Error occurred Bad request. (InvalidChangeBatch 400: CharacterStringTooLong (Value is too long) encountered with '"default._domainkey 14400 IN TXT "v=DKIM1;k=rsa;p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC9LPp1DUrKuStMOP9c1SU1mK.... .....