I admire your skills and imagination. I've had my eye on an old milking churner at my father in law's farm as an ideal DIY barbecue base, but don't have the equipment or skill to turn that into a reality.

One thing I've learned about charcoal barbecuing, having watched a lot of Weber-based videos from the US, is the benefit of having a bottom wire section to put the hot coals on, above the cooking level.

Fitting a rack below your cooking level to put the hot coals on would help the air fan your coals. Having hot coals lying directly on the bottom of the barbecue pan is nowhere near as efficient. As you've noted, they can't breathe.

I also bought a charcoal chimney burner thing sold by Weber which is dynamite. Can't recommend it enough. With just some scrunched up paper/or fire lighter and a match, you get the coals to red hot embers in there first, then tip/spread them on the cooking layer, and you're into it.

Nothing beats a good charcoal barbie in my opinion.

I've cook on it already three times it works ok but imo needs more air flow.

I'm already working on it and decided to add a door.

Few pic of the grill 

   

First burn-off, 5kg of charcoal.

 

some more burning-off :)

Malaysian chicken satay. Works well with anodized grill grates 

Voila, dinner is served... but where is the beer you ask