Please pull those spindle bearing adapters off and inspect their ID, and the OD of the mating area on the spindle journal, to see if any wear.
IMO those bearing adapters are a poor method to make a disc brake retrofit, as they create an additional interface surface that is never used in an OEM design.
They would need to be super-precisely machined on hte ID and OD (on the order .005 or less?). Not easy to do on such a thin-wall, multi-diameter item.
If those adapters have any movement vs the spindles (like ratcheting slightly with every brake application) they could be wearing.
If they are press-fit or Lock-Tited, perhaps it's OK.
But if it's metal on metal with a slipfit (like the ID of a bearing race) and the components don't have the right hardnesses, it could be ugly.
I've mentioned this in various forums over the last 20 years, and have never gotten a response from anyone that defended (or could explain) the engineering and/or installation of these adapters.
As you've gotten a car that had the kit installed, you can provide some valuable info.
I have some info on your other questions:
A 3/4" front bar made a noticeable downgrade on my 65 Chrysler when I removed it to repair bushings. So a 3/4" bar with good bushings will help your car noticeably.
If Firmfeel has one that will fit yours, the 1-1/8" size will be even better. (I have one on my 68 Fury)
The PS pump you have involves a rubber bumper down in the bracketry. The bracket at the top has been added by someone.
See this thread, esp post #14, for a good explanation of that engineered bracket setup:
66 New Yorker 440 info