lowering my FG - yeast problem? restarting fermentation?

Hi everyone,
I posted a topic regarding a WLP english ale I received in the mail that I was worried about having gotten too warm.
I pitched it, no starter, into 5 gallons of 1052 wort in the 70's. Primary lasted a few days now it's still and it's been about a week. Only down to 1020.

In the same mail order I got another tube of english ale, so, hoping to restart fermentation a bit and get that a bit lower I dropped it in the still beer.
24 hours later, not a bubble.
SO I shook it a bit.

Basically,
was adding the extra yeast and/or aerating it worth it?
Is there any way to get the gravity a little lower?
Did I just waste a vial of yeast?

in my experience, the only thing that's worked in that sort of situation (assuming that there's still fermentable sugar in there and the yeast just pooped out) is to pitch an active starter (at high krausen). adding more yeast that isn't alreay going full steam doesn't seem to help much.