Accidentally mashed high, sweet beer at 1.020

[beren]

I finally made my Brawler clone but the mash ended up being very low so I added 1gal almost boiling water after 10mins which shot the temp up to the low 160s. This was a mistake as now the yeast stopped but it's still very sweet. Even chilled with some carbonation it's sweet. I was thinking of either pitching a pack of s-05 or adding some amylase enzyme. I've already tried warming the wort from 65 to 72 and there's been no change for a week. I'm using wy1028, London ESB.
OG was 1.050, looks like it's only at 60% attenuation. I got a reply or 2 on Reddit but looking for more thoughts.

 

[dmtaylor]

A pack of US-05 should do the trick. I would keep amylase away from it for now, save it as the last resort option.