My '05 Did something similar but it was because of weight reasons. However my crack was not nearly as defined as yours. What I did was clean and wire brush mine and put a fairly generous bead on the engine side. I did not do under the car just because I didn't want to ruin any clearance for the mount or the Strut. If your really good with shop tools you could make half inch or so brackets and bead those as well, but I think it's not necessary It didn't get rid of my creaking sound, turned out I just needed a new strut mount.

So My Recommendation is remove the strut and get a new mount for it, then clean the top. Throw a bead on it and go about your day. Depending on how good you are with a welder (I am not) I removed my hood. Wish I had pictures for ya, but mine has been traded off.