Larger than the 10 MB attachment limit of most email providers.
I'm unaware that Signal is geographically limited in any way.
Signal is anonymous as your phone number is. PGP isn't anonymous either, so this seems like an irrelevant criticism.
Again, you can obfuscate the recipient as much as you can obfuscate a phone number. You can't obfuscate the email address you're sending your encrypted email to.
This depends on how they use contacts to match users. I believe they only collect a hash of the phone numbers you choose to share with them.
How large?
> several recipients
How many, in what countries?
Is the communication anonymous?
Can I use it in such a way that obfuscates the message's recipient?
Can I send an encrypted message when the Signal servers have been DOSed?
If seized, can the controllers of the Signal servers get the contents of my entire phone contact list?
I believe that Signal is adequate for a small subset of encrypted message cases, but not as a good replacement for encrypted emails.