Just stop creating your own techniques.
Use a very well known, common and functional secret sharing scheme, such as Shamir's (SSS).
Doing your own crypto always fails. Whether encryption or something else doesn't matter.
Professionals in the field of crypto already created several good secret sharing schemes.
You don't have to use Shamir'r secret sharing scheme which is based on polynomial interpolation.
There are other gemoetric schemes or schemes based on the chinese remainder theorem available.
Just use a scheme made and approved by cryptographer.
Don't do your own crypto!
Do you have a link to scheme that is made and approved by cryptographer, that i am able to do with pen and paper and would require 2 of 4 parts? I would be more than happy to use that, but I have not been able to find it.