I would say the slots are not needed 1.9 mm is decent spacing.
The annular ring is looks small on all your pads. IPC for big ones is twice the hole size, so 1mm hole 2mm dia. pad. The relays need more, especially if 1oz copper.
The J1 connector pad holes look unequal and the relay coil too but maybe an illusion or rendering is doing that.
I would consider moving all the low voltage stuff over so you can have four mounting holes. Right now the one corner can bend down, especially when the connectors are screwed or wire torque, so the PCB could touch the chassis. The connector would be in front of a relay.
ULN2003 (5V) maybe get rid of 20 some discretes/resistors/diodes driving the relays, even though some outputs wasted.
Mains relay contacts arc a little and generate a burst of EMI, which is coupled to your logic from the relay coils. Usually a 0.01uF cap from GND to chassis to cover that, assuming a metal box and spacers.