I was given a similar American set made by Sears Craftsman with Mapp gas & oxygen, gives off a good flame that you could braze small steel jobs or silver solder with but at the prices charged for cylinders a proper oxy/propane set would probably be better value. The cylinder fittings on mine look different, the Oxygen fitting is the same diameter as Mapp bottles and the last time I searched nowhere stocked them.
yes if your only doing small parts or tubing. anything larger and u wouldnt be able to sustain the heat required
What do you mean exactly by "braze with brass"?
Brass rod as a filler between two pieces of metal.
An oxy gauge will show the pressure - and by inference the quantity - remaining in the bottle, but the propane will always be a guessing game as it's stored in liquid form. If a pressure gauge starts to show a significant drop it means that the gas has already run out. There are 'gauges' of a sort that can be applied to the side of a propane bottle to give a rough indication of the contents by indicating where the surface of the liquid is, but they only work while gas is being drawn from the bottle.
Normally the flow rate is controlled at the torch which you set according to the flame you need to match the work being carried out. At the bottle you merely slowly crack it open and then keep going until it's fully open to give the best possible as flow.