PS- you will note that in that split master print one of your separation planes is really ripply.
That is an artifact of that plane being very close to parallel to the build platform.
You will get a much better result if you angle the model such that the separation plane is inclined to the platform by at least 45 degrees. ( in the direction the angled faces are running so that ALL the separation planes are at around 45 degrees )
Because this is a split master- you do not need to use the costly high temp resin, and would be better served by an opaque resin like the grey- or the dental model resin so that you can better ‘read’ the surface of the model for finishing prior to pulling silicone molds from it.
Ideally- you want to orient the split master to maximize accuracy of the separation plane- you are less concerned with printing artifacts on the facets of the die.
the reason is because the separation planes of both sides of a split master need to Match and so you want to avoid at all costs having to retouch or alter the separation planes in any way. The surface of the model, however, you intend to polish and refine anyway…
so the printing angle that gets you the most accurate separation plane may well leave ripples or other artifacts on some of the angled planes of the die- but those are surface you plan to refinish anyway.
Ideally- You should create the opposite split master for the other half- and create some additional registration feature on your existing separation plane because the plane you modeled registers to two halves in ONE direction… but they can still slide relative to each other in the direction those angles run.
You will need to keep the CAVITY lined up in both X and Y and the existing planes only give you X.
And one last thing. I made that model as a demonstration from the file you provided. In addition to adding another registration feature… You can eliminate the Ejector port and have that face in the model.
And you should re-position your Gates ( the entry point of the resin you will be casting ) so that you introduce resin at the lowest point in the cavity-( As the mold will stand during casting ) with vents at the highest points… when you are not using an injection press, you need to consider that you are Not filling an empty mold with resin, you are pouring resin into a mold that is Already Filled, with Air.
Plan for the resin you pour or syringe into the mold to flow into the cavity at the bottom, and sweep the air up and out of the cavity ahead of the resin. This will result in better and more consistent castings.