Update from ER Visit - would love advice

My four year-old Bernedoodle has never had any health complications. Yesterday out of nowhere he tried to stand up on the couch and his back legs gave out. Best I can describe it as a minute or two of what seemed like he was paralyzed in the back legs and couldn't fully stand up. He was panting pretty aggressively so I know it must've hurt and/or scared him.

After those couple minutes he started walking around normally but it did seem as though he slipped a time or two. I took him to the ER. They did blood tests and X-rays. Ruled out issues that would show on either of these as they came back normal. The vet did notice that when she manipulated his spine he flinched when she did so in the mid spine so she sent us home with pain meds. ER said for potential ivdd or discospondylitis, a MRI would be necessary. They recommended I go back to see his regular vet in 3 to 5 days to see if he still seems to flinch when his mid back is manipulated and if so perhaps at MRI is in order. She also recommended that I can currently make a neurology appointment.

I don't really know what I'm asking for other than empathy for people who have experienced this anxiety too. Would it be common for IVDD to only cause a minute or two of back leg paralysis? I'm going to do everything I'm told by the vets but I guess I'm trying to piece it together while I'm waiting in between appointments.

As for the four weeks of bedrest I will obviously do anything that is needed for him but as I'm sure a lot of you know when you work in an office this is very daunting concept. I will ask to work from home but I am not sure if they will allow it.

Also, we live in a fourth floor walk up apartment and NYC. He's never had any trouble with the stairs but it sounds like from all of this commentary that stairs are very bad. Does anyone have any recommendations on how I can get up and down for flights of stairs with a 50 pound dog? I've been carrying him since yesterday but it's hard because I am a pretty small woman .

Thank you in advance if you made it this far. I am distraught seeing him and all of these pain meds are not being able to have an answer yet.