^^^ like what @legendlee said...

1, drybox, low relative humid only stop spore from materialize to fungus

2. once materialize, it will not stop growing even in low humid.

only physical cleaning(with alcohol, ethanol (do not use methanol)) can remove it. UV(<400nm) might kill some fungus/algae to some extend only but not the spore, hence spore will still materialize when condition are meet again.

3. yes you can keep fungus infested lens in the same drybox with other lens, because mainly there is not 'active air/moving air' to transport the spore to other lens and the drybox provide low humid that doesnt meet the requirement for the spore to materialize.