Is that even enough? Considering the size of
chainstate, I'd say 8192 MB
dbcache is better, but OP doesn't have enough RAM for that.
Don't worry too much about that displayed 0.03% per hour rate, it tends to underestimate a lot.
My experience is the opposite when I start from scratch: the rate is quite uptimistic for the first hours, but becomes slower once it reaches more recent years of data.
@OP: syncing Bitcoin Core is more than just downloading the blockchain. It includes verifying every Bitcoin transaction ever made, which is very demanding for your hardware. An external drive is far from ideal, and it's risky. If you ever accidentally unplug it, you risk corrupting your data.
My advice: decide what you need first. You've also opened a topic about Electrum, which works great on your hardware. Or
prune the blockchain if you don't have a specific reason to keep all data.