I was on lamictal for 4 years at 300mg and had similar issues that you did with respect to language and typing.

My doctors at the time said my symptoms are related to the depression I'm experiencing, which is my main problem. I thought they were wrong.

I had to stop lamictal suddenly due to a bad reaction and I'm on different meds now. And guess what, I still have the same problems. They're not as bad as before but they're still present. And I'm still depressed.

I cope by practicing words through writing and I have a grammar checker installed on my computer. The grammar checker catches the mistakes you mentioned and I take note when it does to try to learn about my mistakes.

Things are slowly improving. I noticed that my writing is getting better faster than my speaking is, but I do happen to write a lot more than I speak.

I've been off lamictal for 3 years now.