The largest diameter on the tool that will come into contact with the workpiece is what you should use as a guide for rpm. So in your case start by treating it as a Ø1" cutter or a Ø1" drill. Then as stated above feed at a speed and depth of cut that cuts without rubbing or labouring the machine.
If you have a low power machine you can do the height in two parts, cut the top half a little less than final dimension. Remember this will not be the same point as the final dimension with the tool down to the bottom of the dovetail. Then do the bottom half taking the last few passes to final dimension over the whole of the machined face.
Another option for a low power machine if you have a suitable cutter is to take out the bulk of the material with a woodruff or tee slot cutter, saving the dovetail cutter for the remaining material.
Martin C