Need help with CB radio set up.

Please let me know if you need more information.

I bough a CB radio Cobra 29 LTD classic.
First set up was a single antenna, with mirror mount (on passenger side), the electrical source was provided by the factory one installed in 2024 Freightliner Cascadia. SWR readings was directly from the CB radio.

However, with barely being able to hear anyone unless “SUPPER” close I have since changed things up.

I bought an external SWR reader.
Chanel 1 = 1.4
Chanel 40 = 1.8
New power source is wire ran from fuse box positive and negative.
I now have two mirror bolt antenna mounts (driver side and passenger side) with a divider coax cable.
I left the external SWR mounted up (figured it could stay on).

Now all I hear is static (I don’t hear anyone with new set-up, with the exception of one time on channel 9 for two seconds). However, the squelch and RF gain do not need to be as high as it was with previous setup to reduce the static.

I need help

Sorry if this is long or if this is a silly question supper new to CB radios (we all have to learn some time)

please see attached photos.
https://imgur.com/a/mk6FMhT

Thanks all!