BNCs are certainly the way to go as opposed to PL-259

If you keep your eyes open, you can get real RF patch bays. I don't
know the name of the connector, but they are really patches, i.e. no
threads. About the only way to buy these RF patch bays is with the
patches at the same time. There seem to be two similar designs, but the
dimensions are not quite the same. I ohmed out all the connectors
before buying any of the patch cables. The whole deal about about $30
to $40 a few years ago. Mine had the stickers on from a radar company
(Whistler), so I'm pretty sure it was 50 ohm. I guess there is a risk
you might get a 75 ohm video patch bay.

Unless the pre-amp is as clean as your radio, I'd take the loss in the
splitter and make it up in the AGC. I wouldn't want to risk intermod in
the amp degrading the reception of the signal.

Signal strength and quality of the signal are not always related. You
can experiment by taking a strong signal and pad it down with an
antennuator to the level of some weak signal. The padded down strong
signal tends to sound cleaner. I think this is because the pad also
reduced the level of the background noise at the same time, while a
weak signal has a lower signal to noise ratio "naturally." I hope that
makes sense.