Don’t worry about grammar. That’s what editors are for.
1. Would you believe a lawyer who told you to go to your interview at the firm in your underwear because they’ll tell you the dress code after they hire you?
2. If an editor is holding one fresh, engaging story in each hand and one is clean and the other riddled with grammatical errors, which do you think she’ll buy?
You’re helping keep down ever other romance writer on the planet by taking a low advance.
If you believe the publisher you’ve chosen will right by your books and help you grown your readership and your career long-term, then you’ve made the right decision for you. Every other romance writer on the planet isn’t going to come to your rescue when your buzz-worthy deal crashes and burns you with a 30% sell-through, so let them negotiate their own deals.