It's gonna be tough with a pot that small...you'll have to do a late extract addition, and I'd imagine getting 6# of DME to dissolve in 1 gal of water will be tricky...it'll be the consistency of tar.
Here's what I'd do: figuring the recipe was based on a 3-gal boil, and you're going to boil about a third of that:
Bring 1 gal water to 160F in your pot
Crush the 0.5 lb Crystal malt and add to pot (in a grain bag, if you have one)
Hold 30 minutes, remove grain (pull out bag, or use a strainer if you just dumped the grain in)
Add 2# of the DME and boil
Hop as scheduled
10 minutes before the end of the boil, add the remaining DME
Transfer to fermenter filled with 3 gal boiled/cooled water, top up to 5 gal.
That should keep your IBUs in line, since your boil gravity is close to the recipe intended.
I pretty much blew through my hobby budget getting the initial supplies.
I'd argue that you haven't got your initial supplies yet, with a pot that small. Rather than fussing with the above, I might drop $15 on something like this
. You can also find aluminum pots in that size/price range, and occasionally cheap SS too.
Not worth risking a $40 batch by not spending $15-20 on a pot.
Also, make sure you use the 2nd recipe...the first is a partial mash, though it doesn't say so.