Computer Advice to Meet Bitcoin Core Requirements
As I suspected, my current machine (MacBook Air, lol) is not going to work.

That really depends on what model you're talking about. Modern Macbook Airs are definitely powerful enough.

It looks like I only have 61 gigs of 120 available disk space.

That's more than enough for running Bitcoin Core in pruned mode.
When pruning is enabled, old blocks are deleted from disk a while after they've been verified. This disables some functionality, but is equally secure - everything is still fully validated, just not kept forever. It doesn't interfere with normal functions.

I honestly don't even know how to check the read/write speed.

It's the speed of the disk. All new disks can do more 100 MB/sec, but for initial synchronization (the time your node needs to validate all of history) an SSD will be a lot faster than a spinning hard drive. Don't use an external drive connected through USB - such hardware is not designed for the kind of heavy database load Bitcoin Core causes.

an unmetered connection

That just means you want to make sure you don't pay per megabyte for your internet connection. Bitcoin Core will be downloading several 100 GBs of data from peers (all old blocks), so if you have to pay for that, you may want to reconsider.