Your descriptions of your son suggest that he has a language-based Learning Disability and possibly a receptive/expressive Language Disability. He also sounds as if he has ADHD.
Loretta Cozza is a special education administrator in New York State. She has extensive experience working in middle and high school settings and came out of retirement to continue supporting schools in need of guidance. She is currently serving a combined middle and high school setting in a rural district. In this interview, she talks about some of her lessons learned around supporting students with LD, partnering with families, and mentoring other administrators within the special education setting.
Studying a foreign language can be especially challenging for kids with oral and/or written language learning disabilities. The International Dyslexia Association looks at the kinds of problems students with both moderate and severe LD might manifest in foreign language classes, and lists some approaches teachers can employ to assist these learners.