KOH or NaOH plus CaO (lime, quicklime, calx, burnt lime)is the advised drying mixture for ammonia
CaCl reacts and MgSO4 sucks ammonia up together with the water. (Same for methylamine, btw). Drying tubes are better longer than thicker, also they should provide a significant slowdown in gas velocity for to make uptake of water easier. So the free volume in a filled drying tube has to be more as in the tube before and after it. Dont press the drying agents in the tube but take a bigger (longer) one.
There is no condensing of water at all wanted! It would suck up ammonia in huge amounts at once. To produce as less water as possible (low temps in reaction and slow motion) and to adsorb the rest is the way to go. So go direct in a sufficient drying tube which may be mounted to the precooler. This results in a compact design and a temperature gradient which makes sense.
The final condensor should be made of metal for the heattransfer properties. NO COPPER! Black iron does fine here, is asscheap and easy to work on as it can be epoxied and has by no way to be welded. (choosing a epoxy usable at these low temperatures is understood)
Surface area is whats needed so rough surfaces beat polished ones. After the condensor a tube should run to near the bottom of the metal made, precooled receiving vessel so after some ammonia was made the outlet is below the surface of liquid ammonia. This way the production can get speeded up significantly after a slow starting phase. Also a astonishing small condensor sufficices in this setup where the receiving flask is also utilized for liquidification purposes.
Starting to cool the parts in time, say several hours in advance is a very good idea. A high humidity on the working space sucks up unavoidable ammoniasmell. Better inside a garage and boiling some water beneath as outsides in dry air which takes the smell over miles.
Methylamine is a cake in comparism to ammonia. What problematic is seen in a compound having a boiling point of -6,5°C is hard to understand. A look over the fence to the Birchers might be a good idea - anhydrous methylamine gas is not hard at all, neither to make, to store and not to use.