RF splitter resistor placement and 0 ohm resistor RF test port question
While the alternatives you're considering will affect the performance slightly, the differences will be small.
On the signal splitter, there's not a lot you can do about that triple pad in the middle, it's probably as good as it can be without proper design as it's shown. You could probably improve the performance slightly with some detailed modelling and measurement, but with 6dB loss, would you notice? You'll be using physically smaller components, with pad width commensurate with the line width, if you are serious about improving the performance.
If that is really a signal splitter, so one into two, then you may be better off with a 2 x Z power divider, rather than a symmetrical 3 x Z/3, it should be easier to tweak up the design performance if the loads are suitable.
The difference between 45 and 90 degree bands will be much less than simply going through the connector. It's a debug connection, so you will be making allowances for the uncertainties in your measurements.