I have really f**ked up at work, lost my company thousands of dollars

Point out that you said from the start that it was going to end badly. Sounds like your boss can't admit fault. Put in a formal complaint against him.

You knew this was coming: -
https://moviechat.org/general/General-Discussion/6484de204599f00df19a352c/Should-I-quit-my-job-due-to-my-inexperienced-supervisor

Just say you gave the customer what they wanted, what they asked for and what they agreed to, despite your objections, and that the customer is ALWAYS right.

From the way you've described him, your manager sounds like someone who will probably want to chew you out. But if he has any common sense, he would also want to work out what went wrong so as to prevent it from happening again. In relation to the first point, you can cop the vitriol. I know it won't be easy but after he lets off some steam, he probably won't hold it against you because it was a mistake.

But regarding the second point, you can admit how you got the task wrong according to your responsibilities. Instead of trying to blame the colleague before you, you can emphasise that you didn't properly check the work already done and discuss what you will do to get it right next time. For example, if you can think about any training you can undertake, he might find it reassuring. You can also discuss strategies you can think of to do the task right next time.

I know this sounds strange but a lot of managers want employees who can admit they've fvcked up because they're not going to hide problems on future occasions. I hope it works out for you and either way, it might be reassuring to remember that everybody makes mistakes in their career. Every day in workplaces across the world, employees and employers are having these difficult conversations when the sh1t has just hit the fan.

Just quietly take responsibility, apologize and accept whatever the consequences are graciously. However, being yelled at isn't generally acceptable, so if he goes on a tirade, just calmly state that you understand you messed up and if being fired is the consequence, then you accept this consequence - and then leave, don't sit there for like 20 minutes while he rages. It's also good to have a list of ways you're going to fix this/rectify the situation/make the best of what happened. If you don't have that, maybe you should just leave - idk what day you're on, but you could put a stop to the meeting altogether and just say all this upfront beforehand and hand in your notice.