I'm guessing here, big time. World-class WAG...

I'm not sure if Intex is still using the 1.25" hoses or have gone up to the standard 1.5". Nor do I know if they have standard returns or their own. If the wall is soft, that's a special kind of return. If it's a liner against a hard wall you should be able to use a standard return.

Splitting isn't that tough. You'll just need to use some Schedule 40 PVC fittings. There are tee fittings that split the flow. IF you have 1.25" plumbing, increasing to 1.5" may be enough to reduce the pressure.

There are 1.25" internal fittings (the hose slides over them and is clamped) that screw into 1.5" PVC. Be sure to use lots of Teflon tape and you MUST use at least Schedule 40 fittings.
I actually have a couple of Tees in my system, one to bleed off water to my solar panels and the second to split the flow to each of two sets of panels.

Again, this is all guess-work without being sure.