1st AG red with big gravity

For my first AG, I chose the American Red recipe I found from a member here.
I had the exact WLyeast it called for washed in the fridge, so I made a 1000ml erlynmeyer starter 2 days prior, and went for it.
Now I had tested the MLT for heat before doing this, and it held temps great, and I noted loss. What I did not test was the keggle boil off. I was certain the little bayou burner would struggle, but no. I made 6.25 gal of wort, and ended up with 4 gal after cool down!!!
When I checked the gravity, it was 1.070 !!!! It was supposed to be
1.052-54 . I pitched the yeast, and called it a night.
This was Monday night, and the starter is doing it's job trying to blow the lid, airlock, blowoff hose....anything I put on it, so I;m happy it can handle the wort, but will the yeast be able to finish the gravity down below 20?
It's WLP004 Irish Ale Yeast.

I was thinking about boiling another 1.5 gal, chilling, and tossing that in, but
afraid to disturb the process, or contaminate my first grain batch. Maybe when racking to secondary?

Any thoughts appreciated.
Thanks.
Karb

Obviously your OG is higher because you only finished with 4 gallons. If it's fermenting now I wouldn't mess with it. I fou want to drop the abv you are on the right track. Boil some water then let it cool, put a gallon of it into your secondary, then rack your beer.

WLP004 should not have a problem fermenting to below 1.020 from 1.070.