Walt could have turned himself in after killing Krazy 8.

yeah, but that would have been boring

how would he pay for treatment/leave money for his family?

As Walt made clear later on....
He was in the 'Empire' business... Even if he hadn't realized it at the time.

And then he’d have to explain what he was doing out there. Plus he wouldn’t have been able to leave the money for his family that they needed

Still wouldn't explain why he was in Jesse Pinkman's basement with Krazy-8 chained to a pole (that fact alone would have eliminated self-defence as a legit excuse). Or, following the line of questioning and assuming Walt told the truth, what the two of them were doing with a makeshift lab in an RV out in the desert in a less-than-ideal situation with a drug dealer. Either way, Walt's family would either have had to scrounge for bail or he'd spend some time behind bars.