In the morning with a fresh eye and mind I realized that I could epoxy this broken clip after the connector was mated together. Yes, this connector does snug. With this clip reattached it prevents the assembly vibrating apart. For added strength I wrapped a loop of electrical tape around just for the clips. I did have zip ties in mind, but after this light bulb moment it seemed unnecessary.
ATTACHED BROKEN CLIP WITH EPOXY *AFTER* MATING CONNECTOR
ELECTRICAL TAPE REINFORCEMENT AFTER EPOXY CURED
Unfortunately... this weekend of work did not get my left turn signal to light up. Thankfully, all the exterior and interior lights still function normally like nothing happened.
So I guess, with the instrument cluster ground refreshed, and this connector properly cleaned of corrosion, the only thing left to do is remove the gauge cluster and see if that left turn signal bulb and socket needs replaced.
Am I going down the logical path here?
Thanks guys for all the input while I get this issue figured out.