jamb
The jamb bracket was always loose, so I had to keep using longer and longer screws to make it stronger. Over time the wood completely got eroded, left with a gaping hole and no place to insert a screw. How do fix this? I have a young handyman who is painting my house and I was going to have him fix this, but I don't think he knows how. If someone can explain clearly I'm sure he can do it.
Use the extra width to properly hang the door . . . there is no need to disassemble the replacement door jamb.
Adjust the wedges such that:
Scribe all 6 edges of the 3 jambs relative to the sheet rock
'Complementing wedges' are a pair of wedges with identical taper, inserted from opposite sides of the rough opening.
If you don't own a power planer already, here is a google search. I suggest a light weight model with carbide blades that auto-align.
The basic procedure for removing a door is: remove casing, remove screws from jamb/brick mold, and push the door out of the hole, brick mold still attached. Unfortunately your situation calls for some more devious tactics. Because the outer molding appears to be part of the transom casing (assuming you're leaving that part alone) you're probably better off not disturbing it. So you have to remove the interior trim, remove any screws that connect the jamb to the substructure, then very carefully prize the jamb away from the outer molding with a bar such as this:
to keep from marring the backside of your brick mold.
Once the door is out, the problem then becomes finding a new door/jamb that fits the opening not just properly but perfectly in order to get the reveals right, which may be a challenge considering how old and...unique your existing door is. If you over come that hurdle, just caulk the backside of the brick mold with sealant (sealant not caulk) and follow the manufacturers instructions for sealing the threshold and all should be well. Cheers!
Best Answer
As Eric suggested, clean out any loose debris first. But do not use small pieces of wood such as toothpicks (they are usually made from very cheap, low-density wood, that easily crushes when you insert later the screw for the hinge). Get a wood filler (which consists of sawdust in a binder) and fill the gap flush. The filler has a much higher compressive strength than matches and toothpicks (around 400kg/cm2, or 5600 PSI). Then drill normally and fasten the hinge as you would with a new door.
Edit: regarding the comments below about brittleness, I personally recommend Abatron WoodEpox. I used it several times, and I can guarantee you can drill into it.
Edit 2: In their website they say it's designed to be able to drill into it. Source: https://www.abatron.com/product/woodepox/