Being in a romantic relationship with someone with multiple disabilities

I'm looking for support in my relationship with my partner. He is dealing with chronic pain, lasting effects of traumatic brain injury, and is diabetic and recently started a low carb diet.

I really love this person and when he is feeling good I love the way he pampers me, I love doing sports activities together, and I love how smart he is, always teachinge things, supporting me to be better whether diagnosing and fixing my car, working on my interpersonal communication skills, cooking, etc. He opens my world to new experiences. We have planned 6 months off traveling in foreign countries before coming back home and traveling in an RV to explore and find a new home to live in USA. We are preparing now. I am so excited about our plans, seeing this as my ticket out of an unhappy life I can see myself struggling through in our expensive city working at low pay unfulfilling jobs.

Since we are starting this journey so soon, there is a lot of stress, and with his multiple disabilities, it is very difficult on me to put up with his mood swings and the stressful conversations about the trip, and having to plan things and get work completed in a short time when he is needing to be reminded of things, and he gets overwhelmed or tired. I can't find the line of assertiveness that keeps me from being a nag but also keeps us on track from knowing we're behind and stressing. I want to have a harmonious relationship!