bld, I am just lurking on this thread, reading it to see how things work out - hope they do for you.
I noticed your choice of breadboard; good choice. I have one of these and it has lasted me almost 20 years now. However, in the future (near future, if you are doing a lot of playing) I would suggest spending the money to get the "larger" breadboard that has something like 3-4 of these smaller boards, plus power bus strips along the top with power binding posts, all mounted to a metal plate. Having the larger area to work on is a treat, and well worth the money spent. You could, of course, build your own version of this from the smaller boards if you need something larger (but expect to pay a bit more).
Also - you will likely find that the relays, while sized 0.1 inch to fit the PCB board you have, probably won't make contact with the breadboard's pins; the relay leads/pins may be too short. Even if they are long enough, they may be only "just so long" - so you put them on the breadboard, and it looks like it is working OK, then it stops because you nudged one or something. IE - it can lead to headaches trying to determine what is an intermittent fault due to the contacts barely touching each other.
So - do yourself a favor and when you get to that point, solder the relays (and shunt diodes) to the PCB, and run temporary connecting wires back to the breadboard for testing.
Something else which is useful during testing and later after installation is to hook LEDs up to the input side of the drivers (in your old system that would be between the Arduino and the ULN2803; in your new setup, beween the Arduino and driver transistors), with an appropriate current limit resistor - if you size it right you can use a single resistor on the base of the transistor to drive it and the LED at the same time without causing harm to the Arduino. You just want to use a resistor to give you enough current for driving both, without exceeding the output capability of the Arduino (keep it somewhere around 20-30 ma).
Having such an LED in place will give you visual verification of the circuit working, even if you can't hear the relay clicking or are too far away - or if the relay or transistor fails. It would be a little piece of hardware debugging tool.
Good luck with your rebuild - I think you were really close last time; it would have been better had you started on a breadboard instead of a PCB. Oh, one other thing for the future as you build a project - if you use DIP ICs on a PCB, put them in sockets (and add 0.1uf caps across the power supply inputs for filtering). Sockets make it easier to repair the circuit in the future should a DIP IC fail; after you have isolated and fixed the reason for failure first, of course...
