So I had been a bit hesitant to post on this thread that I started, since the thread itself took a big turn away from the original topic. It's been almost 2 months since the original problem emerged, and now that I'm halfway recovered, I feel like it's an appropriate time to update those whose who have offered their generous advices and insights.
Long stories short, the ISTP guy is no longer a part of my life, nor are his housemates that I used to hang out with all the time.
Maybe partly due to the cold weather and muddy sky of the northern midwest, the house was no longer a friendly inviting hangout place.. instead it had turned into a grey stagnant tension-filled house where everybody was mad at each other for one reason or another (this includes undone chores, one guy mad at the ISTP guy for hooking up with me, etc.).
The ISTP guy was no longer his interesting self. He had lost any will to live like a normal college student, smoked all day and did nothing. I was ok with being patient and waiting out to see if things were going to get any better. But then, he decided to switch his attention to another girl that shared his kind of lifestyle, and lied to me about it when I questioned him (since he was the one who explicitly stated that it was something more than just friends with benefits). Between doubting myself and doubting my ISTP guy, I hit an emotional low during the months of January and February, to a point where I felt the need to just walk away all together. I wrote some messages to people at the house, including the ISTP guy, and have not been back at the house ever since.
At the time, making that decision to walk away seemed like a reasonable one. But it was the emotional aftermath that got to me. One minute I was bawling all in tears from being hurt and being lied to, another minute I was telling myself that it was just a FWB relationship, and I cannot blame him, so I should just suck it up and move on and act normal. After an especially draining month, I was finally able to nail down the source of my grief, which were my lost friendship with people around the house, and being lied to (and played by) the ISTP guy.
Lately I've been able to forgive things more, and my overwhelming desire is to be back around the house and be just friends with everyone, like it used to be. But I know I've done enough of what I can do, and I can only act on my desire if they reach out to me (and clear the air).
Again, thank you so much for everyone's support, it definitely helped me put things into perspective. It's still very hard because I saw the relationship with this group of people that I placed immense trust in slowly deteriorate into nothing. I lost a great genuine friendship with T (one of the guys that liked me) for someone who played me and threw me out the window (the ISTP guy). I hope we can someday patch things up together and move beyond the past, but until then, I will have to suffer the aftermath alone myself.
Some things are harder to see over the internet, like when someone says something with a twinkle in their eye. 
. Chin up sweetheart, and if T is a genuine friend, the friendship was never lost. 
