What I like in the new house and what needs to be fixed

As I wrote before, we recently bought a house and I can call myself a homeowner for the first time. The house is gorgeous inside and out and I'm so excited about upcoming projects. But as much as I like a lot of things, there is a lot of work to fix, add and renovate.

You can watch a tour of the video here

So what things do I absolutely love in this house?

First, it has so much charm and so many cute little details, like this ring bell on the front door.
It's in great shape, considering the age (122 years!!!)
I love the library and build-ins, the wall in the closet, and the drawing room. I love the size of the master bedroom, although I never cared about that.
This house has tons of windows, and I think I can say that each room has at least 3 windows, including two windows in the walk-in closet! Who would've thought?
It has an unfinished basement with so much potential!
Multiple built-ins throughout the house make a lot of storage space.
A round porch that wraps the house from the front
The landscape has so many trees, including a little creek on the property

This list can go on and on. Besides repainting rooms and making some interior design decisions there are certain things that require attention.

Things I'd like to change

There is no garage! With my line of work, it's crucial for me to have a workshop, and adding a garage could help increase the value of the house. I'm running into some difficulties with the placement since the most logical space to put it, on the driveway on the left side, has septic tank fields under it. So I'm preparing for a battle with the town to get a permit there. This won't be easy
The house is very old and doesn't have central air. Long gone are the days of my childhood when we lived without AC. So we are planning to install it first thing. We already talking to contractors to get on it immediately.
I'm not a big fan of a closed-off dining room and considering that there is a closed-off staircase between the dining room and the kitchen, I'm wondering if it's possible to take it down and make an open kitchen concept. This is still in the works.
Since the house was built in 1900 and it seems people were shorter back then, the staircase to the second floor has never been changed, so it's super low. I'm not even worried for the kids as much as I'm worried for adults. So this will be definitely one of the first projects I'll need to tackle in the house. The staircase is not up to code in the modern days, but since it's original to the house, it can be here. When I'll redo it, I need to account for the new codes and make it at least 36"(I think that's the correct size)
The zip code for the house is great and kids will go to a good school but this house is located at the intersection of two busy roads and part of the property is missing a fence. I already see myself getting so paranoid when the kids are outside if I don't get on it right away. So I hope I'll be able to tackle it this summer.
Half of the windows are single painted so I'd like to eventually change them to make them more environmentally friendly and energy-efficient. This project will be a massive undertaking. I counted all windows and we've got 20 newer windows (in the additional rooms that were added in the 2000s) and 25(!!!) old windows. I mean it's great to have such a bright space but I'm already scared of the quote we will get for replacing 25 windows.
There is a bit of mold in the basement in the room that I planned to renovate into a gym. The floor is covered with linoleum that has to be completely gutted out. So I want to get on it soon as well.