Most people don't check in at the airport anymore so your boarding passes printed from home are perfectly fine to use. I would say that boarding passes printed from home and the mobile boarding pass on the phone are the most commonly used boarding pass these days anyway.
If you traveled from the US to Europe, wouldn't you as an American have a stamp in your passport for entry to Europe?! If so, you can use that as proof if you can't find the boarding passes. And what about when you returned to the US, did your wife still get a stamp in her passport? If so, you can use her passport as well to show proof of your trip together.
If you have a lot of other proof for your removal of conditions, I wouldn't even bother with the boarding passes from that one trip unless it's to show how you visited your wife's family in Europe?!
You can work freely. The EAD is the DHS authorization you need to work and your SSN will not change. Its yours for life. You're good to go!
If you want the verbiage removed from the card, wait until you have your GC on hand and request a replacement at your SSO. It won't matter though what the card says - or doesn't say.
Tanti auguri!!
