1) I tried to share my calendar with my wife 5 times by sending her an email at her Hotmail account but her account never received the emails.

2) I tried to share my calendar with one of my alternative email addresses.  I got the email immediately at that address but when I tried to accept and open the calendar it told me the permission had expired.  I guess whoever I share with has less than 30 seconds to accept.

3) I tried to just using the calendar sharing URL but that comes up as an invalid URL on any browser or machine where I try to use it.

It seems the fix is to not use Microsoft's calendars and use Google calendars.  At least you can export the Microsoft calendar as ICS and import it into your Google Calendar.