Everybody, thanks very much for the condolences. They do help.
On Sunday, I was thinking about a bit from _The Heart of the Mind_ by Steve and Connirae Andreas (civilized NLP, recommended) about intractable grief being related to thinking of the lost person as remote, and that it's possible to think of them as close. And I had an experience of contact with something--it was happy, not angry with me, and seemed to be Ra, but if so, he was rather more of a personage than I thought. This was all in feelings--nothing visual. The only thing I'm sure of is that the universe and/or inside of my head are more benevolent than I usually think.
It seems to be on a separate track from my wishing that I could have handled a number of things better.
I do feel relieved--dealing with Ra's not using the litterbox reliably, the need for more maintenance, and the likely monetary costs were all hard on me, and that's no longer a problem. I don't feel bad about feeling better.
twistedchick was very firm with me last night that I needed to do something nice for myself. I interpreted that as "unusually nice" (in retrospect, it didn't have to be) which made it difficult--I do such pleasant stuff as is available in the house anyway, and I really didn't want to spend money. Weirdly enough, getting all my mail orders out in a timely fashion does count as doing something nice for myself, and I hope it also works as a hint to the universe to send me more mail orders.
I am a civilized enough person to have had a polite discussion with the vet--but uncivilized enough to have contemplated showing up with a dead cat in a plastic bag.
In any case, I should have been given a factsheet with the drug--I'm pretty sure I wasn't. I might have been so fried I dropped it in a bag and forgot it, but I'm such a compulsive reader that it seems unlikely. Also, Heather (who's almost as compulsive about reading in general and more compulsive about reading directions) doesn't seem to have one from the meds she picked up earlier. The vet is very concerned that I didn't get a factsheet.
Weirdly, drooling (which Ra was doing) is a clear stop-the-med signal. Falling over and not getting up for five minutes isn't.
Those two meds are typically prescribed together, and she's never heard of it resulting in death. I've found a web page for vets which endorses the combination. A fast googling didn't turn up anything suggesting it was dangerous.
The reason I picked the bethanechol a couple of days after the visit when Heather got the other two meds is that the vet had it specially compounded--it was the lowest possible dose and Ra was a little under the weight recommendation. The vet was expecting to need to ramp it up.
 Neurolinguistic Programming--a system of psychology based on the idea that everything people do makes sense in terms of how they represent things to themselves, and they can behave and feel better if they have more accurate representations. "Civilized" because the first book or three by Bandler and Grinder had somewhat about controlling other people's representations without them noticing.