Your physio does appear to be doing all the things that I would be doing. I'm unsure I can give much more advice without examining the toe.#
In terms of toe exercises it seems that self mobilising was helpful... continue that. you can try ultrasound, icing, and taping.
Also look into strengthening the toe using rubber band resistance perhaps and stretches following that. - Ask your physio if they feel that will help.
The big toe is supplied by the lower spinal nerves so your physio should clear that area of your back (L5) to assess no spinal component.

Am still in UK till the 19th. Currently in Birmingham with colleagues for NYE party. it's been good so far. visited Bath and Oxford which are beautiful cities.... I can't say the same about Birmingham - I apologise if your a brummy. I also apologise for calling you a brummy if your not.