Jjust scroll down to where it says about crossover.

Well i had a friend of my look up the info on my deck and the way the deck is setup is. The front and back speakers run off the high pass and the sub runs off low pass and that is why there no option to pick from since it is already set for you you just have the adjust the slope and the frequency. So for your question yes its 31Hz low pass with 24db slope

That is entirely way too low. It should be in the 60-100hz range for most typical systems, depending on your system and preferences. Also, it would appear you are using both the lowpass in the amp and in the headunit....while there is not something technically "wrong" with this, in your case it's probably a little unnecessary. My advice would be to increase the lowpass filter setting on the amp as high as the knob will go or simply shut it off if at all possible, then reset the lowpass crossover on the headunit so the crossover frequency is somewhere in the range I previously listed.

So by turning my lpf on my amp all the way up and setting the lpf on the deck around 60-100Hz that will disable the lpf on the amp. If so what about my slope should i leave at 24db or go lower it can go down to 0db.

Yes, you will be effectively bypassing the crossover in the amplifier.

You can play around with the slope, see what setting you like best. 0db is equivalent to "off". 24db is fine, but try the different settings see what you like best.