1. There is mental and physical issues, however there is no specific disorder.
How much time are you spending away from work to deal with these appointments? Consideration can be made for additional support to cover the impact on your income. The courts will consider it but, you need to have a very detailed schedule of appointments and the medical encounters (medical records) to backup the time spent addressing your family situation.
I would put together a detailed schedule (if you don't have one already) of the appointments, with who and dates and times. You will need this evidence to demonstrate the impact to your earning potential for the additional support.
2. The other parent has always been the secondary care giver. I have done the majority of appointments and all surgical appointments. We live a couple of hours apart now, so he isn't that involved in appointments. Doesn't ask how things are, rarely acknowledges emails when I send information. I was going to ask for sole custody, but don't want to get into an expensive court battle. So not sure if this is wise.
With regards to how medical decisions should be made. They should be made in consultation with the other parent and the medical professional. In the event of a disagreement you should have final say on the treatment but, it should require confirmation with the other parent by the medical professional.
I recommend this because the other parent needs to be responsible and aware as well even if they are not participating. Furthermore, if there is a delay in medical needs of your child you can make the decision without the other parent but, in guidance from the medical professional(s) involved in your child's care.
I will try and give you some clauses in a bit of how this actually is legally worded. It is very complex and rarely seen in agreements or orders.
3. We don't seem to be needing acute care any longer, a few years back this was an issue, but currently and in the future I don't see that being an issue.
A clause has to be put in to protect you and the other parent on decisions made in an acute care setting. You don't strike me as a high-conflict person (nor has your description of the other parent, the other parent seems "avoidant" more than conflictual). Basically, you need wording that if there was an acute care situation and your child was with either parent you could make a decision but, in guidance of the opinion of medical professionals treating your child at the time.
The complexity is that you want to clearly identify "acute" versus "long term" care in this situation. Acute care situations require fast decisions and the other parent may not be able to assist (can't contact etc) and you both need to be able to make a decision if the other parent cannot be contacted in a reasonable time.
4. Health care is covered for the most part by a health plan, probably about 15% isn't covered. There will be special extraordinary expenses for some drugs, and equipment that isn't covered.
15% of a large number is a large number. For example if you require a power assisted chair and accessories... 15% of that can be a big number.
Depending on the household income supporting your child's needs you may qualify to work with a variety of different charities who can help fill the gap. (I.e. March of Dimes, etc...) You can always explore these options but, it takes time to get into the fold of these organizations and get the support and help they can provide.
5. No nursing support is required. We do need specialized babysitters, as there are toileting issues, and safety issues.
I am assuming that the other parent is going to require this support as well even possibly on a every other weekend access schedule. This is a major and complex S7 expense potentially. So long as the other parent understands this (which I hope they do) then it shouldn't be a challenge to reach agreement on this. Of course any expense incurred would have to be backed by a medical professional and at the level of quality of service recommended by the medical professional.
For example, I have seen a case where a parent went out and purchased a power chair, sought a large sum of money from the other parent to cover the chair but, the medical professional was of the strong opinion that a manual chair was better (and it is cheaper). That is why it is important to insure that you work with the medical professionals and the other parent to understand *why* the expense is being incurred. To be special and extraordinary you should have the support of the medical practitioner for the expense.
Good Luck!
Tayken