Grammar is not gross

I have come to a rather large obstacle with my heritage Spanish speakers. We respect each other, we enjoy our time together, they are open to new experiences in the classroom. However I cannot figure out how to successfully reinforce proper advanced grammar, good spelling and accent use for the life of me. This is an especially painful point for me for two reasons.
1. I LOVE GRAMMAR. All those rules are just so cool and make sense and Spanish is so lovely in that way.
2.  Their poor spelling and continual anglicisms make them look far less fluent than they are. In spoken speech, they can run circles around me. But put a book in their hands or ask them to write a formal letter and their comprehension and writing is years below their grade.

What do I do?
First and foremost, I ask your advice. Anything you might have to offer would be so very appreciated. Please add any ideas in this Google Doc. It doesn't just have to be for Spanish learners. Any technique is welcome, although I do prefer not to go the drill and kill route.

Here is a basic list of things that I have tried. I'll be honest, it seems like their spelling and accentuation are getting worse.
1. We read a lot. Things like The Hunger Games, People magazine in Spanish, the news, etc.
2. We have free journaling daily.
3. There is a list of approximately 30 words that are our "It words," things like "he hablado" instead of "e avlado" and "más" instead of "mas." We've had it since the third week of school. They still don't know it despite repeated testing, grade consequences, textual reinforcement, competitive memorizing activities, etc.
4. I have taught "traditional" grammar lessons.
5. They have taught each other grammar lessons.
6. We have repeated and reinforced old grammar lessons.
7. I've taught them college-level phonetics and dialectology in order to help them better understand the use of various letters.
8. I've gotten angry.
9. I've let it slide.
10. I've graded meticulously to show each potential improvement.
11. Everything in my class can be redone. Everything. So if they receive a poor grade for bad spelling, they can rewrite it for full credit.

Clearly, I'm at wit's end. I very much look forward to reading your advice and I cannot wait to convince my students that good grammar is not gross.