I agree with Peter H, seal the lower concrete walls and floor. I think you have enough cracks in the physical structure to be able to install a
solar attic fan to remove the moisture in your garage. But it would be best if you can add soffit venting or a vent in the door.
Installing an
expanded metal gaurd on your window might add some extra protection from vandals, but not fool proof. You can also block off the window and add a
solatube for lighting. These work great.
I noticed from the staining on the floor and wall that you will get water inside the garage. Sealing alone may not prevent this. You may have to dig a trench under the rear window and the left side and install a french type drain. You will have to drill a hole in the retaining wall to allow the water to exit. Not easy, but it will help keep the moisture to a minimum. As it stands now, you get all of the drainage from your garden behind the window, trapped at the wall with no place to go but the garage. This would be a great time to waterproof the exterior walls too.
The patch on the walkway looks useless to me. I would remove it and reseal the area against the wall. Even applying some bitchathane and a flashing would be better than what you have now. It would look better too and remove the tripping hazard you have now.
These are all things that you can do yourself or with limited help to keep the expenses down.
Installing solar fan. The attic fan and solatube are probably the only high cost items, unless you hire out the french drain. Install the fan now and do the rest when you get the money and time. An alternative to the solar fan is the
turbine fan. The
attic fan information guide may help you decide what you need to do, although you are doing ventilation for the entire garage, I think the material covered will help with this installation too.
From you pictures it looks like the old knob and tube wiring system has been removed and you have no electricity to the garage. Thats' why I recommended the solar fan and solatube lighting.
