I think most mums that they sell around here are hardy. They have been forced to bloom early to be in the store. When I've planted them, the blooms turn brown and I shear them off. If they are hardy, they will stay green all summer and come back next year and bloom.

Image is too small. However you can apply a per-emergent herbicide such as XL or Amaze mid-Feb., mid-May and mid- September to prevent them germinating in the first place. Here is a link that might be useful: XL

Weed and feed is regular fertilizer plus herbicide. You should get the same fertilizer effect from the product. The issue that most of us have with the combo product is that it is fairly rare to need to fertilize and use a blanket application of a weed killer at the same time. We prefer to get the appropriate product and use as needed, when needed. Fertilizer will promote weed growth just like it does with grass. If there are weeds germinating and not killed with the herbicide in the weed and feed, those weed will grow. Ideally you want to fertilize then hit the weeds later if/when they growth.

That may be torpedo grass. For any kind of creeping grass, a hard barrier is necessary to keep it out of unwanted areas. A row of bricks or landscape timbers is enough for most grasses that try to go up and over. If it is torpedo, a surface barrier may not be enough because it will go under.