So i bought a 2 foot screw stake and a heavy duty 20 foot tether made for dogs between 150 and 200 pounds. I twisted the stake 3/4th's of its length into the ground and bought Colby a harness with double leash hooks that hide the break away-type clasp so she cant pull out of her collar

Basically, i got it because Colby seems to enjoy being outside a lot and so far, the whole set up works great. Mind you, this DOES NOT replace her regular exercise runs and bike rides [which i recently found out she loves more than scything else we've done so far], but she just seems so... bored when she lays around inside and when she's outside, she just looks happy overall [posture and such].

But at the same time, even though its proven great so far, it's only been a couple days. I keep the doors open and i have it positioned so i can see her all the time and i did a strength test on the stake with a couple people [all at the same time] and it didn't so much as budge. But I'm afraid to move away from the spot where i can see her [when i'm not outside with her] because she did get away from me once and i ran almost a mile before i caught her. So it makes me super nervous,

Do you think this is a safe way to let her have some time outside without having to worry every second someone's not with her? Is there something i should add? Is there a better way? [fencing in the yard isn't an option. We go have a fence on one side of the back yard, but the other half is marshland and is protected by the federal government, so we cant even put up a fence. and yep, we asked, lol].

It sounds like you have a nice set up.
I, myself, have 6 huskies outside on tethers as they loath being in the house. I usually have them running loose inside the fence that surrounds the area where their tethers are but they can't be loose when I'm gone or not able to keep an eye on them. I also like to use a long tether in the back yard so I can bring the huskies back, one at a time, to join while I have a bonfire or do yard work.

So as long as there's nothing she can get tangled on, has access to shade and water, yadda yadda, you get the idea, then I think it's fine. I'm sure she will enjoy lazing around in the sun during the day, I know mine do.

My 2 go up front on leads all the time. Long as it is strong enough (yours is) you can leave them out, just glance out to make sure they're not up to no good.