Noises right after an oil change are not a super good sign. Being three weeks away, could just be a coincidence. Lifter tick is coming from possible oil pressure issues (clogged oil passages). Hopefully the shop has experience with the 1ZZ-FE engine, as even in good running condition, they are pretty noisy engines. Lots of valvetrain chatter and thrashing from the timing chain.
You are right to be concerned about the rod knock. The metallic thrashing noise after you lift off the gas pedal definitely sounds like rod knock - you can double check by running the car up to 3000 RPM or so, then very slightly feather the throttle (drop RPMs 500 or so), if you get that back rattle noise, almost sure to be rod knock (assuming you discounted all other possibility for noises).
Lucas and other oil additives like it, change the viscosity and possibly boost your additive pack. Some use moly or zinc in suspension to hope that it sticks to the bearing surfaces to cut down on direct metal to metal contact. This will only be a temporary solution, as the bearing is continue to deteriorate. I'd definitely recommend getting used oil analysis done on the car ASAP, with the oil that is in it now. Find out if there are elevated wear metals and/or coolant in the oil. If it comes back clean - dump the oil and filter and use a fresh OEM filter and spec'd oil viscosity for the engine (no additives). You want to find out if the noise was caused by oil starvation (collapsed or damaged oil filter) or if the car doesn't like the oil you are currently using.