An EBB will be fine. The issue with “vertical dropouts” isn’t with vertical dropouts, it’s with using a chain tensioner (as required on 99% of frames with vertical dropouts, ie those without a BB or sliding/rocker dropouts).
The braking forces thing isn’t an issue either. That’s just a factor for a front disc brake, where the reaction to the braking force is downward on the axle. On the rear a disc brake is mounted at the downward-moving part of the rotor so the reaction force will try to push the wheel upwards into the dropout. The only other brake related issue is when using track ends (ie open to the rear) with a brake mounted on the seat stays, when the reaction force will tend to push the wheel backwards.
When braking a fixed gear through the chain none of these are issues: the force from the chain will tend to pull the wheel forward, but then the force from the ground is pulling it backwards, so it’s all fine.
So crack on.