That broad leaf weed killer is not meant to kill off grasses, so it will not control this grass. Unfortunately anything that you can use to control this grass will also kill off the more desireable grasses you have.
How does this grass spread? Only by seed? By root? Both?

I did a little bit more search online and found the following description most resemble what I have in my lawn. Looks like a tough weed to deal with. Thanks for feedback.

Here is a link that might be useful: I think this is what I have

A good discussion of bentgrass vs nimblewill in the following post.

Here is a link that might be useful: bent grass vs nimblewill

How brainwashed have we become to believe that a 2nd type of grass growing in a lawn is a weed?