Custom redaction patterns inconsistent in Acrobat Pro DC -- what "flavor" Regex to use?

I have several large files filled with addresses, phone numbers, SSNs and several other information that needs to be redacted. I've tweaked and customized the Patterns XML file, and several of them work fine.

However, the addresses patterns I've created are not working at all, or else capture too much, although they test fine in other Regex editors. The issue seems to be problems with certain characters or phrases that Adobe doesn't like -- for example, this script:

^(\d+) ?([A-Za-z0-9](?= ))? (.*?) ([^ ]+?) ?((?<= )APT)? ?((?<= )\d*)?$

It works great in Regex101 for testing addresses, but Adobe doesn't even recognize it as an line. I believe the issue is the "^" at the beginning. 

Can anyone advise what "flavor" Regex Acrobat uses? I can't find this info anywhere? Or is there a way to use characters that otherwise cause issues, like "<" and ">"? Any help would be much appreciated!