is there a way to make objects only interact with objects and not sackboy, and vice versa? is it possible for a dephysicalizsed object to be bounced upon by the springinator?

There should be an ignore sackboy option on the dephysicallizer, but if there isnt then you could put a tag on the player with a broadcast microchip, and set it to ignore that tag, either way, it is possible

There are many possibilitys with the phisycs tweaker.
When you want to climb behind the ladder then you will use it.
Like putting invisible material behind the ladder.
Putting physics tweaker and make it interact only with dummy tag.
Make it climbable with material tweaker.
Since it is not dephysicalized, you will jump through and still be able to climb.
Just play with different tweaks until you find the right ones for you.