Did you/vet discover what was wrong with puss?
Just in case you didn't, here are a few random ideas from my experience.
The kind of vomitting you've described isn't typical of furball, they usually deliberately cough when they have this, rather than being overtaken by the vomitting. However, if the furball, or other obstruction is severe and low in the intestines, it can cause this sudden vomitting.
The nature of what is produced is important. Is it undigested food? That indicated obstruction, in my experience (usually furball, which I treat with tinned fish in oil, or furball treatments).
However, tumours can cause this type of vomitting, especially those in the intestines or chest.
If the cat is producing a more liquid form, this indicates serious infection, or other condition which would have lead to serious deterioration by now, noticeable in the cat's general health, weight, energy (basically he'd be on last legs). This doesn't seem likely.
Are his ears hot? Your vet should have noticed any temperature (thermometer up bum).
Samantha made a hobby of this type of vomitting at one time. I went through the rigmarole of furball treatment, worming. The vet's only suggestion was a change in diet. Then I noticed that it occurred when she ate rabbit flavoured cat food. They only have chicken varieties now.
You cat needs x-raying for blockage, and tummy palpating for tumours/serious furball.
Maybe a change in diet is needed.
Is the i/d an intravenous drip? You can rehydrate the cat using a feeding syringe filled with water (and lots of patience).
Good luck.
It may just be a phase, as it was with Sam; she was about the same age.
P.S You can check for dehydration by lifting up your cat's scruff, then let it go. It should spring back into place. If it remains standing for a moment, your cat is dehydrated.