A 12 gauge low voltage wire has a diameter of roughly 0.0808 inches (2.053 mm), whereas 14 AWG wire has a diameter of around 0.0641 inches (1.628 mm).

 

So finally my eBay-sourced Hozan P-706 crimping tool arrived from Japan. Looks very nice. Have not tested it, but it is a quality tool. About $80 USD landed cost with taxes/brokerage fees imposed by FedEx (Mail would have come thru tax-free).

I have not had time to order new connectors, but I did get the AliExpress-sourced key set for terminal removing. That one was about $4 USD landed.

Just need to get the connector pins and plastic connector housing on order when I have time. From somewhere where I do not have to order 1000 at a time.
It has been so long ago, I have to figure out the correct sizes and where to order from again.