the lime juice shouldn't hurt anything else in the tank as long as you spray it directly at the mouth of the apstasia anemone.
It wouldn't be enough lime juice to change the PH in your tank.
If the apstasia is to big to retract back into the rock, you could burn it with a sodering iron.
For the straw, you could use super glue.
if it spreads your best bed would probably be, getting some pepermint shrimp. They'll eat apstasia and make sure it doesn't come back.