Spouse Visa: Final Application Questions!

I apologize for the detailed questions here and am wondering if any kind soul would be able to provide feedback. I hope it's okay to post such specific questions and would really appreciate anyone's response!

I have 3 questions while completing the Spouse visa application form:

1) "Have  you ever received medical treatment in the UK?"  I answered "Yes" because I visited a private clinic once for a minor illness.  The application asks for supporting evidence demonstrating that full payment was made. This may be a stupid question, but is an invoice showing a zero balance considered acceptable proof? There are so many inane requirements for this visa, and I just want to make sure that is all they will need. (As opposed to a signed, embossed, certified letter from the head of the clinic, blue signature, two witnesses, etc etc etc).

2) "How long have you lived at this address?"  - I'm giving my parents' address, which has been my permanent address in the U.S. for almost 20 years. However, I've also lived abroad in various countries for the past 10 years and recently returned to the US. Should I put "9 months" or "20 years" ?

3) For "Travel History" should I list as "visits" countries that I lived and worked in? For example, if I worked in South Korea for 3 years, do I list that as "Visit" "Purpose: Work" or is that considered being a resident, not visiting? Do I list each time I came in/out of the country as a separate visit? As it is, I've listed all my entries/exits while working abroad and all the vacations I took, so I've got over 65 travel entries because each trip in/out is listed individually, even when I was resident in a foreign country. Have others done this?

If you've made it this far, thank you for reading and for your thoughts! I apologize if it sounds like I'm being overly technical, but I'm paranoid a small mistake is going to lead to a rejection so I want everything to be perfect!

I apologize for the detailed questions here and am wondering if any kind soul would be able to provide feedback. I hope it's okay to post such specific questions and would really appreciate anyone's response!

I have 3 questions while completing the Spouse visa application form:

1) "Have  you ever received medical treatment in the UK?"  I answered "Yes" because I visited a private clinic once for a minor illness.  The application asks for supporting evidence demonstrating that full payment was made. This may be a stupid question, but is an invoice showing a zero balance considered acceptable proof? There are so many inane requirements for this visa, and I just want to make sure that is all they will need. (As opposed to a signed, embossed, certified letter from the head of the clinic, blue signature, two witnesses, etc etc etc).

2) "How long have you lived at this address?"  - I'm giving my parents' address, which has been my permanent address in the U.S. for almost 20 years. However, I've also lived abroad in various countries for the past 10 years and recently returned to the US. Should I put "9 months" or "20 years" ?

3) For "Travel History" should I list as "visits" countries that I lived and worked in? For example, if I worked in South Korea for 3 years, do I list that as "Visit" "Purpose: Work" or is that considered being a resident, not visiting? Do I list each time I came in/out of the country as a separate visit? As it is, I've listed all my entries/exits while working abroad and all the vacations I took, so I've got over 65 travel entries because each trip in/out is listed individually, even when I was resident in a foreign country. Have others done this?

If you've made it this far, thank you for reading and for your thoughts! I apologize if it sounds like I'm being overly technical, but I'm paranoid a small mistake is going to lead to a rejection so I want everything to be perfect!

Good questions. 

1- They are really looking for and unpaid NHS treatment here. Even though you went to a private clinic, I would still include the invoice with zero balance, just to be safe.

2-I would probably put 9 months because from the travel history, they will see that you have been living elsewhere. You can explain this answer in a cover letter if you want to. It won't make a difference with the application but it never hurts to explain and will lessen your worry.

3-Is there any option to put that you were a resident of another country? If not, then put visit, purpose work. Does it still ask for 10 years of travel history? If so, then that's what you should give them. Continue on a separate page if the system doesn't have room for all of your trips.

Thank you SO much for your time. It's fantastic to have another perspective on these questions, and it validates what I've been thinking!  I appreciate you!

For the travel history I put together a spreadsheet of every trip for 10 years and another one of every visa including visitor and work. Like you I worked and travelled all over SE Asia, Australia, HK, NY etc.   
It is a lot of work but I just gave them all the detail - that was on the advice of the Immigration Barrister I used for my wife's UK Spouse Visa.
If you want to do an absolutely perfect job, put it on a spreadsheet, then write a statutory declaration, have it stamped by a lawyer, with the spreadsheet as an exhibit.  I did this - it was probably overkill but it is then unequivocal.

Good luck