The short list worth giving him is what means ring emergency services. Fainting, real difficulty breathing, chest pain, anything more than mild discomfort. If he can't tell uncomfortable from frightening, treat it as frightening.

Past that nobody here can advise you specifically, me included, and I'd be wary of anyone who tries. Health conditions or anything you take regularly, that's a doctor conversation before you plan anything.

tell him out loud that hes allowed to make the the call even if you're sat there insisting youre fine. easier to sort that now while youre calm.

the thing is youre the one person in the room who can't see yourself from the outside. thats true of anyone whos ill with anything, its not you being unreliable.

Tell him its fine if it turns out to be a quiet uneventful evening and he mostly watches telly. that's not him failing at the job, thats the job going well.