James, you had many good comments! I am a microbiologist by training--slow learner with 10 years of college! Spores are the problem and when they get in the lungs with the moist-warm environment, can start to grow. However, our bodies meet many insults every day and we survive.
Once the wood is dry and coated, it is very stable and the number of spores is very low to any consumer of food from the bowl. Many foods have spores as part of the package--cheese. By ingesting food into the stomach, the fungus is quite harmless. The main danger is with the dust in the air you breath getting into the lungs in sufficient number to cause a problem. You want breathing protection of the hepa filter to take out 1 micron particles. The vaccuum hose can pick up much of the dust but it will come out the original 30 micron filter bags on the vac. Therefore, it is dangerous enough to pay attention to how you work with it or don't do it.

I could be mis-informed, but I'll take a stab at it.

The spalting process stops when there is not enough moisture in the wood. So, if you dry it out you stop the spalting (because the fungus dies...or does it just go dormant?). I believe you can also stop the process by making the wood too cold or too hot for the fungus, so freezing it or boiling/microwaving it.

Anyway, somehow the spalting is stopped in your wood. Then you're going to turn it and the dust will have dead/dormant fungus mixed in with it. This is bad for your lungs and can also hasten a developed allergy to dust and/or the wood species. The drying that occurs during turning stops any spalting that might have been going on unobserved deep inside the piece.

After that, of course you sand which is an even worse exposure to the dust. If you're doing a lot of spalted pieces you should consider getting a powered respirator and an ambient air filter. (I have neither yet but that doesn't stop me from preaching!) Also, clean up after you turn because the dust left on the floor and shop surfaces is still dust laced with dead/dormant fungus.

So, after all that, you have an awe inspiring spalted bowl that needs finish. First, it could be a decorative bowl, but then you wouldn't be asking about food safety. So, it's intended to be a utilitarian bowl for fruit, salad, or something.

That means a food safe finish like salad bowl finish, oil, or something else which is allowed to cure for weeks so that the petroleum distilates can evaporate out.

After that you've got a protective layer over the bowl. If this layer is uncompromised it should be safe. If you were to use the bowl as a cutting board, be jabbing forks into its surface, or constantly washing the bowl (or throwing it into the dishwasher) then you're putting holes and/or wearing away that protective layer. At that point, the spalted wood, with its dead and/or dormant fungus, is exposed to your food. Putting the stuff in your body through your mouth is bad, whether you're breathing it or eating it.

So, my take on it is that if you're going to limit the bowl use to light duty (and especially if you're going to freshen up the finish with new oil or something once in a while) then it should be fine. If you're not, then just make it a decorative bowl!

The other way to look at it is that there are lot worse things carried on pollen or in the dirt you accidentally rub your nose with while gardening...it's all relative.

Good luck!