I used jmp.chat so my daughter could have a phone number for calls and sms on her wifi only tablet, then set her up with signal. Worked great, good customer service. Sms is a little weird because the receive address isn't just the phone number, it's more like an email address, but it works. Thanks for the list and detailed pros and cons! 

 If you use the Cheogram app, you can sms just like normal, you don’t need any weird addresses