"Incapacitating" is the native English expression (1,240 hits for "incapacitating disorder" vs. 98 for "invalidating disorder" - and all appear to be non-native English. I have never heard the word "invalidating" in 30 years of medical translation.

With or without comma. We don't need to use "and" with premodifying adjectives in English. The comma is sometimes used if the two adjectives are considered to be too similar in scope.

Examples:

Its legacy, Gulf War disease, is **a complex, progressive, incapacitating multiorgan system disorder**. The symptoms include incapacitating fatigue, ...
www.ratical.org/radiation/DU/

**Progressive, incapacitating cerebellar dysfunction** occurs in most cases, and no treatment .... cerebellar disorder with ataxia, dysarthria, and nystag- ...
doi.wiley.com/10.1002/(SICI)1097-0142(19961115)78:10%3C2153::AID-CNCR16%3E3.0.CO;2-Y -

**pulmonary fibrosis known as silicosis a progressive, incapacitating and sometimes-fatal lung disease**. Silicosis is. characterized by generalized fibrotic ...
www.agripacific.com/VendorStuff/MontereyChem/msds/GranusolM...

A 84-year-old man with **progressive incapacitating back pain** over the preceding 3 months before visiting our institute. On examination, his groin and foot ...
www.jkns.or.kr/htm/fulltext.asp?no=0042008025

It is a rare disorder caused by mutations of AGPAT2 gene or BSCL2 gene. .... and cystic angiomatosis with **progressive incapacitating bone involvement**, ...
pt.wkhealth.com/pt/re/oooo/fulltext.00043790-200801000-00025.htm;jsessionid=HTHSnZpPqmh50216vppwxLMx8f4cy