So, perhaps the problem is that you can't cut the pattern you want with the tools at hand rather than you can't cut the pattern you want.
Time to buy that wet saw you've always wanted?
Or maybe your local tile shop would make the cut(s) for you?
One thing I've found to work with really bitchy tiles (not all will cut with the same ease) is to lay the tile on a piece of carpet when cutting. That would be with either the angle grinder or on the wet saw. Dampens the vibrations that result in the break at that narrow junction.
The difference in diamond blades for the angle grinder can change the whole dynamic, too.
And when push really comes to shove, sometimes drilling a small hole at the apex of the cuts can prevent the breaking.
Or you can cut two pieces if you're happy with that.
My opinion; worth price charged.