Help me save this Monstera

Morning all!

I have this Monstera that's been growing through my staircase. When we moved into this house, it was a super happy plant quickly filling the space with enormous leafs. Now it's a shadow of itself, as you can see.

Now this MD absolutely must survive and get healthy again. My wife got it over 30 years ago as a tiny single leaf in a tiny pot, from her mother who died rather young already 20 years ago. This plant is a family member with a lot of history.

Here's what I already did:

• I found the soil rather compact and wet, in a closed pot. So I feared root rot. I've now repotted it into a pot with an irrigation system (one of these) with new earth.
• I found some aerial roots close to the pot and redirected them into the pot.

What I'm thinking about is:

• Get a second flower pot on the lower floor (to the right of the wardrobe) and put some of the hanging aerial roots into it, so they can find nutrients.
• Put a humidifier on top of the wardrobe. This is in Germany, and we're just coming out of a cold winter, so I fear the air may be too dry.
• Wrap some of the steel rods with coconut mat so it can properly attach to it.

What do you all think? Am I doing the right thing here? What did I miss? What should I do different. Every help is appreciated!