I believe these dreams to simply be nightmares/dreams that are symbols to what was going on in your life at the time.
The fact that you needed to say "At the time" so much for the first dream makes this apparent enough for me - and while I can imagine the dream, and
how it would be frightening, I think the colour purple, spiders, rejection of food and materials, and a feeling that you're under control (standing
in line, forced to do things, etc) are definite indicators that this dream occured during a stressful time in your life.
As for the second - probably just a crazy dream... you're in a mansion and a rock falls on you
Trust me, I've had dreams about the future... unfortunately for me, they're always really boring dreams.
Most recent was just this Saturday - which was great, as it felt like I was starting to lose this ability (it's been happening with decreasing
regularity since Grade 9 - I am now 2nd year University). I met with a person I only knew on the internet, and after a wargame we went to eat wings.
Whilst we were talking, I realized that I had had a dream about that, with the content that we were talking about - but since I had never seen the
guy, I had just assumed it was a regular dream at the time.
So while my "future dreams" may be rather pathetic - it does occasionally help. For example, in my dream, whilst we were talking, I ended up going
on a tangent and really confusing him. An ability I was able to master in Grade 8 (whilst these future dreams occured with massive regularity to the
point I almost hated it) was to change the outcome of what happened in my dream and what happens in real life. Thus, I was able to change what I said,
and we finished our conversation.
I've got a lot to say on the subject of future dreams, since they've occured to me so many times in my life - even if the events I dream of and when
they happen aren't that important. Their mere existance has allowed me to come up with an awesome theory for how the universe works.
For example - if I have these dreams, and they come true, wouldn't that mean that there's Fate? However, when the time comes, since I can CHANGE
what happens - then that means there's no Fate. However, how could I possibly know what is going to happen 6 months to a year in advance? Especially
with people's appearances that I have never met, or with places I had never seen?
The answer? Different quantum universes. Every action that can happen will happen. If a photon has a quantum probability (caused by when/where/what
direction the emitting photon releases it at) of going through one slit or another, there is a seperate quantum universe where that, and only that, is
different. Of course, since there are nearly an infinite number of quantum possibilities for the near-infinite number of quantum interactions that
occur in our nearly infinite universe every day for a nearly infinite amount of time... that means there's an almost perfectly infinite number of
universes out there. Also, don't forget that different quantum probabilities for those universes also take place (so, yes, there is a universe where
Hitler took over... but there's also another one where he became the world's most popular talk-show host).
So when I have a future dream, my spirit has actually travelled to a similar quantum universe. Thus, I am actually seeing a PROBABLE future, rather
than the ACTUAL future.