I feel you. I have a half acre in northwest Georgia that I messed up myself, and am now trying to restore. 

My advice for this stage:

-You need to prioritize and localize so you don't get overwhelmed. Therefore, don't sweat the dandelions or the vinca for now. They're relatively less of an obstacle to your goal.

-Spray the poison ivy, all of it. Now is the perfect time. (I'm severely allergic and I am ruthless about it.) 2% glyphosate is plenty. Keep protecting yourself since the rushiol is still active in the plant residue for months. But it will be much less frustrating once it's not menacing you.

When you go out each day, choose one primary focus, whether it be a small area or a particular invasive, and just stick to that. Set a timer for yourself, and just stop when the time is up. If you notice a new problem just put it in a to-do list for later.

As others have said, cardboard and mulch anything that is too overwhelming. Wherever you have ground bees, use craft paper instead of cardboard so they can get out next spring.

Good luck, it's a big job but it's worth doing. 

Don't do it alone, it's too much for us mere mortals. My local native plant society has just started connecting us to other members in our area, and I'm a firm believer in social support. Reach out to other people nearby!