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Typically, this will be due to there being too much nitrogen in soil. If the area get fed, be sure that this is not high in nitrogen.

The excess nutrients will leach out over time.

This article will give you more information on the care of the plant:

https://www.gardeningknowhow.com/edible/herbs/yarrow/growing-yarrow.htm

It should regrow. Maybe you could put some fencing or a cage around it to keep the rabbits out.

https://www.gardeningknowhow.com/plant-problems/pests/animals/keep-rabbits-out-of-gardens.htm

Typically you put three in each compartment, then if all three germinate, you cut out two. Since these are so tiny, if there are plenty of seeds, just pop a pinch in each compartment. But remove all but one or two in each compartment after germination.

We don't make vendor recommendations, but that might be a question for your local extension agent:

https://www.gardeningknowhow.com/extension-search

Unfortunately, this can mean that the pile does not get hot enough. If you cannot get the pile hot enough, than you may need to use another method for composting invasive species.

https://www.gardeningknowhow.com/composting/ingredients/weeds-in-compost.htm