TNG says a ship can replace its antimatter.
Liaisons
WORF: The Engineering sections encompass twelve decks of the secondary hull. Deck forty two contains the antimatter storage facility.
BYLETH: What is the mass flow rate of the antimatter replenishment stream to the containment pods?
WORF: Excuse me?
BYLETH: The antimatter replenishment rate. What is it?
WORF: I am not certain of the exact rate.
BYLETH: Perhaps there is someone here who does know the answer. You. Are you smarter than this one?
LAFORGE: Why do you ask?
BYLETH: Never mind.
BYLETH: I wish to see the Bussard collectors. Take me to them.
WORF: This way.
But TNG also had its issues with lines about antimatter.
Coming Of Age
COMPUTER: Last question on the hyperspace physics test. If the matter and antimatter tanks on a Galaxy class starship are nine tenths depleted, calculate the intermix ratio necessary to reach a starbase a hundred light years away at warp factor eight. Begin.
(Wesley is straight in with 1:1. Oliana runs out of time)
COMPUTER: Time elapsed. You now have one hour free before the next test.
MORDOCK: I must admit, Wesley, you have a very fast mind.
WESLEY: Once as I realised it was a trick question, there was only one answer.
MORDOCK: Yes, there is only one ratio with matter antimatter. One to one.
Skin of Evil
LYNCH: Forget the final check. Initiate start-up sequence.
COMPUTER: Beginning check list.
LYNCH: Override. We are going directly to start-up.
COMPUTER: That procedure is not recommended.
LYNCH: Understood. Now. Prime matter-antimatter injectors. Set ratio at twenty-five to one.
Booby Trap
RIKER [OC] We need warp power now!
LAFORGE: Matter-anti matter mixture ratio settings at optimum balance Reaction sequence corresponding to specified norms. Magnetic plasma transfer to warp field generators per programmed specs. Commander, we should be going like a bat out of hell.
Galaxy's Child
LEAH: The matter-antimatter ratio has been changed. The mixture isn't as rich as regulations dictate.
LAFORGE: Experience has shown me that too high a ratio diminishes efficiency. I worked with the mixture until I got the right balance.
Chain of Command, Part 2
JELLICO: All right. Worf, prepare a series of five hundred antimatter mines with magnetic targeting capabilities.
WORF: Aye, sir.
If they'd brought Worf to the DQ, they wouldn't have had much problem replacing a thousand torpedoes per day. Tuvok should be roughly as competent. He just didn't want to be disrespectful to the captain and say "I'll show you 'we have no way to replace them.'" out loud. TNG also shows Welsey playing with antimatter efficiency and replacement for school projects. After that, it's safe to assume it's readily abundant for all sorts of ideas once you locate a supply of it to farm or mine.
It's also safe to assume
When situation is normal: You can create a matter-antimatter warhead.
When your ship is being digested by a huge organism and your energy reserves are depleted: You cannot create a matter-antimatter warhead.