Help me understand crossover settings pls!

I spent a ton of money on good quality audio components, from Focal, JL, Hertz Mille a ton of sound deadening, closed cell foam the entire truck etc.
I'm running the

$295 Rockford DSR1 8-Channel Interactive Signal Processor w/Integrated iDatalink Maestro Module

Rockford DSR1 and just can't get this thing to sound good.

Currently the best sound is when I run the crossovers "flat" and it's just slightly better than the stock stereo was, just with more bass.
Now obviously this should sound "immensely" better, it's just that I played around with the crossovers on the amps as well as DSR1 and just can't get it to sound good. Full disclosure here that I have no idea what I am doing.

My questions are these:

1.) Should my amps be set to "Full" for the door speaker components and just let the DSR1 control everything? Or should I set the amps crossover to match DSR1 settings? I'm running the 3 way front Hertz mille, door speakers, door tweeter and dash speaker.

2.) For the crossover settings on the DSR1 for the doors, should I use the "Bandpass" option in the DSR1? From watching this video it looks like it should be set to bandpass? https://youtu.be/gTYBcxkbRRU?t=3402

3.)If bandpass is the right option here, what should I set the low pass and high pass frequencies to?

4.) Finally for the subs, I'm running the JL stealthbox with two 10" subs. What should the crossover look like for this on the DSR1 and how should the amp be setup?

Thank you!