When I suggested a large value capacitor, I did not mean at P7. The data sheet is clear that P7 should not exceed 3300 nF. My reference to a large capacitor was to put it on the rectifier output across C1.
I find your schematic is not drawn very well and is hard to follow. Does the primary power for the controller enter at TR1 and TR2 (13VAC)? What is I2? It looks like it might be a 5V linear voltage regulator.
As for the pcb design, the first question I must ask is how the connections are made from J5 to the relay RL. The motor power contacts should be very well isolated from every other conductor on your control board. By well isolated I mean with no metallic contact to your board conductors or planes, no overlap to your board planes, and at least 5 mm clearance (preferably a lot more clearance) to other traces and planes. If it were me, I would not bring the motor power onto this board at all, I would use an off-board relay to guarantee good isolation.
A 1HP ac motor, depending on what mechanical load it has, can require more than 5 kW of momentary power to start. I would use a very substantial (ie. large) relay to switch such a motor on and off.
If the current drain of the uP alone (and its I/O) is small you can put a small series resistance and large shunt capacitor in line with the 5V rail to the uP to act as an additional filter. If your total current consumption from the 5V regulator is small, such a filter is best placed on the input side of this regulator so that it's voltage drop has little effect.