Hi, from what I've read about the sweet william (or Dianthus as it is sometimes known) it grows about 18 inches tall and you should keep the dead flowers
picked off to encourage further blooming. I can't find anything about them toppling over but I don't think staking it will harm it. There are items made for tall flowers
stakes; it is a long stiff wire type stake with a loop at the top made for holding up the flower
. You might check at your local nursery or go to www.michigan
bulb.com and in the accessories group look up plant
Now for the hyacinth. I don't believe you killed it. I have daffodils all over my yard and they unfortunately
get mowed down quite often. (I've really got to stop letting my husband cut the grass
)The biggest problem I have encountered is that in cutting down the foiliage before it dies is the plant
usually won't bloom the following season. There is a method for "forcing" bulbs such as hyacinths to grow in pots indoors. If you can't find anything on the net I will e-mail you the info I have if you are interested.
I do hope I haven't been too "windy" in my response and that you find some helpful info in what I have written.