How do I view what Reminder and Expiration dates I have selected for an envelope? These are open documents, and I didn't write down the advance options I chose

When envelopes are created they use the default set for the Account. So if the default is set under Admin Console > Reminders and Expirations, every new envelope should use these values by default whether creating one envelope or 300 using bulk send.

Unfortunately if you sent out 300 envelopes and the Reminders were set to 3 days, there is no way to my knowledge to bulk change all 300 envelopes to say 5 days instead. You would need to correct each envelope.