I spoke with my sensei tonight, and I'm going to skip this Sunday's test and wait until May to test for black belt.
I've lost too much ground with my current illness; sensei said he wouldn't be able to sleep if he sent me to the test and I got hurt because I wasn't in condition.
The plan is:
1) Get healthy.
2) Improve my eating habits. On days when I'm training in the evening, maybe have two meal substitutes/small meals in the evening instead of a dinner soon before training, and then some protein afterwards.
3) Get back to class and train regularly.
4) Cross train by doing bag workouts, including sprint-like punching/kicking sessions. This substitutes for the interval sprinting I used to do to prepare for competition/testing, and which I can't do anymore because of plantar fasciitis (painful soles of my feet).
I would have gone if my sensei said I should, but I'm relieved I'll have more time to really prepare.