Looks like you have a diamond-in-the-rough!
RE: ASH CATCHER
For an old kettle, see if you can still get the old-type ash catcher. (See previous post about "classic" brownie). Or, maybe you can form a new one and have someone make a pattern from one of their old ones? Old ash catchers were a "dished" piece of flat aluminum, with hook-shaped notches in 3 places. To remove, you would lift and rotate, which would disengage the notches from the legs. Only problem was they would sometimes get knocked-loose and/or rattle-around in the wind.
RE: CLEAN-OUT
In the old days, you really did not need to fully clean-out the charcoal dust after every cook. We would do it about every 3 cooks. However, new K seems to produce more ash/dust. In between, when the grill was cool, we would just poke-out a lot of the dust with a stick/dowel in each hole - the dust would fall into the pan.
For full clean-out, we would:
1. Klunk the charcoal grate around, to knock the loose stuff / small pieces through.
2. Remove the charcoal grate
3. With an empty ash-catcher, open the bottom vents open 100%, use a plastic garden trowel (hand shovel) to stir the ashes around, forcing the stuff through the vent holes and into the charcoal bowl.
4. Carefully remove and dump the ash-catcher