Transaction prioritization

Hello everyone, thanks for stopping by and taking a look at my post.

I wanted to figure out how miners pick transaction that they are going to process.
I know, gas, but stick with me:

10 days ago I sent a transaction with a 70 gas. Today gas reached 56 gas. Why did it not take my 70 gas transaction? How does time factors in miners process to pick transactions? Is is just a game of economy of resources? Looking for a transaction so far away from the current ones is just too expensive?

And a second question:
If I line up two transactions, nonce 1 and 2. Will transaction 2 only disperse to the blockchain when the tx 1 gests done or does it waits for the first one to be processed then it goes to the blockchain? I'm pretty sure that it goes out when its lined up since etherscan picks it up. The issue here is: Is it impacted by the same factors that did not let my transaction on the issue above to be processed?

Thank you very much for taking the time to read and I'd love to hear back from you guys