Two common themes stand out throughout your post:

1) Dysfunctional communication

2) Rumination.

Starting with the dysfunctional communication: It seems there are a lot of communications and expectations that aren't making their way to you. It's reasonable for your manager to buffer some communications from above rather than dumping a firehose of everything on to you, but this sounds like you're missing out on important information relevant to your job.

However, you now have some clarity into these communication gaps. Use that to your advantage. Next time there's a question around a deadline being pushed back, ask specifically why it was pushed back and what your skip-level manager thinks about it. Did they push it back because you were originally behind progress? Or did they push it back because it wasn't needed as quickly any more? Don't speculate, ask.

There's another place where you need to ask for clarity, largely because your manager isn't great at it: Performance management:

> After our meeting, my manager and my boss had a meeting with just the two of them to discuss the status of our project. I have no clue what happened in that meeting and I haven't heard anything about it from either of them since.

Don't hesitate to ask your manager for clarification about expectations. You can ask for a quick chat to recap the project. Explain how you were confused about why the project was considered late if the deadline was pushed back and ask for clarification. Ask how you should proceed in the future. Ask what's expected of you (or employees in the company in general) for positive performance reviews. Again, don't speculate. Ask.

The second problem in your post is heavy rumination. It's natural to feel disappointed in this outcome, but you cannot let it eat you up. The more you let this control your thoughts, the more it's going to negatively influence your work, which could lead to more disappointment in an unhelpful spiral. You must avoid this at all costs.

Some examples from your post of what I'm referring to:

> I'm happy, but I can't stop thinking about that meeting. I really did work hard, so it's demotivating that it feels like the result of me working hard is unappreciated.

> I'm not thinking of quitting over this or anything, but it seriously bums me out.

> I don't know if I have a future at this company

> I'm thinking that now they probably feel that they could fire me if they wanted and not lose much.

> I wanted to make them happy to have hired me, and now I feel like they probably aren't.

It's very natural to feel disappointment, uncertainty, and concern. However, how you react to these feelings will dictate your path in the future. If you let this demoralize you or, worse, start bitterly resenting everything about the company, it's not going to end well.

Acknowledge that this is a mere stumbling block, but it doesn't define your job or even your career. It's a learning experience, but it's not the end of the road. If you take it in stride and use what you've learned to iterate on communication and delivery with your next task, things will go much better. This may feel poignant to you, but I guarantee everyone else is going to completely forget about it by this time 6 months from now.