Words that you can use other than witnessed are seen, observed, watched, viewed, and noticed. These are synonyms of witnessed.
I witnessed a murder.
Jellybeans 2010
It is a foster child, but one word could be adoptee.
Other than strengthen, the word could be reinforce, fortify, boost, or toughen.
U.F.O's are a commonly witnessed phemomenon.
We've just witnessed a miracle.
witness/ witnessed observe/observed
I cannot think of any way the word 'everywhere' could be used other than as an adverb.
A synonym for "you" could be "one" or "they" depending on the context of the sentence.
"Storage" is a word that rhymes with "cartage" other than "garbage."
Ghee, oil, oleo, shortening are the other words which could replace the word butter or margarine.
i think another word could be gossip