yeah worm would deal with that.
what tyre/rim?
Some will drop off, some wont. I have found my dt swiss rims really good, even the road ones. I used to carry co2 for this purpsoe, but stopped as i don't really need it
Yeah the valve will have got a bit glued with sealant, just use a bit of force.
It was about a 4mm piece of flint. Mini bottle of sealant now on shopping list!