{{msg-mw|Payflowpro gateway-error-msg-js|notext=1}}

That is currect - as stated in an earlier topic, IIRC. The code contains "payflowproGatewayErrorMsgJs + currField"

I've translated "The following field is required:" because in Galician "your" could be "o seu" or "a súa" depending on the noun which is next to it.

It would also have been possible to move the translation of "your" out of the first message and into each of the others.

Yep! Did precisely that.