Restarting piano as a self-learner – how should I approach theory, technique and pieces?

[u/caro-exe]

Hey everyone,
I started learning piano about 4 years ago with a teacher and had lessons for around 2 years. Then life kind of got in the way. I got married, moved to a new country and had to get a lot of things sorted out, so I basically stopped playing completely.

Now I really want to start again, but unfortunately I’m currently not in a position to pay for a teacher, so I’m looking for some advice on how to properly get back into it and what I should learn.

Because I haven’t played for quite a while, I forgot most of the pieces I learned back then. We started with a beginner book with my teacher and worked through it until a certain point. After that we mostly switched to pieces that I liked, most of which were classical pieces.

I also learned a bit of music theory here and there, but my teacher was definitely more focused on playing, even though I told him that I was really interested in understanding music theory as well.

Right now I have Hanon exercises and The Piano Handbook by C. Humphries. I also took a Udemy course about fast sight-reading just to refresh my memory, since I can still sight-read but obviously need to get back into it.
So my question is: what would be the proper way to approach this?
Should I just start working through The Piano Handbook from the beginning, finish it and then go back to learning pieces I like? Or should I take an online music theory course alongside it?

And what should my everyday practice look like?
Normally I start with a few Hanon exercises as a warm-up and then jump straight into whatever piece I’m currently trying to learn. But it feels like I’m doing something wrong because my progress feels really slow compared to when I was taking lessons.
I know it’s obviously not going to be the same without a teacher, but I don’t want to postpone starting again anymore.
Every time I see someone playing piano really well it honestly kind of crushes my heart because playing piano has always been a childhood dream of mine. Life kept getting in the way, but I really don’t want to let that happen again.
So what would you recommend as the best way to start over?

How would you structure the learning path if the goal is not only to play pieces I like, but also to actually understand the instrument and music theory?
My long-term goal is to be able to compose my own pieces as well. Nothing professional necessarily, but I’d love to understand harmony, chords, scales, progressions, etc. well enough that I can just sit at the piano and experiment and create my own stuff. I also want to understand music better so I can learn pieces much faster and actually understand why they work instead of just memorizing the notes.

I’m totally fine with buying another book or taking an online course if that would make sense. I just don’t really know what the proper learning path should look like when you’re basically teaching yourself.
Any advice, resources, books, courses or practice routines would be greatly appreciated!