I mean they have already explicitly figured out exactly how many missiles it generally takes to destroy a SD. That being around some where around 500 per ship. So they used like 500k+ tops and considering canon Spindle, and that they have access to their Real Time control they'd probably use less. But yeah your right that they do use hundreds of thousands missiles in book 13.A Rising Thunder specifies that Honor has 25,000,000 missiles at the battle, with 2.5m ready to launch. We don't get any details on how many missiles are fired, but considering she just says "FIRE", we can presume a huge chunk of them are.
So yeah, they have 25 million missiles just at the ready.
I clarified exactly what I meant, so there's no reason to argue about it or pretend you didn't know what I meant. As someone else pointed out, at no point are any of the battles even in question, there's no intended tension about them (hence me calling them 'victory parades' figuratively), the only tension is if the bad guys killing themselves spitefully to frame Manticore will cause any lasting trouble.
As for Filareta.... there's no reason to make him a child rapist to make him a fire and forget missile. He was going there on his own. Hell, he's not even the one who is the fire and forget missile, as it is his tac officer IIRC who is actually under Mesa's control and launches the missiles despite him deciding to reasonably surrender in the face of 25,000,000 missiles. It's just thrown in there at the last second so you don't feel bad that he's about to get blasted and blown up with millions of missiles.
Supply issue does cause the Manticorians to not use missiles in that Wormhole battle and causes a Manticorians squadron to be weak enough that they can do a "heroic sacrifice" and causes the Pov Solarian bureaucrat to order an attack on Beowulf.