vipinsingla, welcome to the forum. Please start your own thread and introduce yourself to everyone!
Marmalade, you are on a steep learning curve! Might I suggest that you bring another person with you to your next GI meeting, have a list of written questions, and plan to spend a lot of time asking as much as you can come up with?
Not everyone who gets Crohn's gets fistulas, but if your brother's disease has that pattern my guess is that you are at risk, too. Keeping the inflammation under control is a good way to prevent fistulas, but I am not sure it is a certain prevention.
You need to find out from your GI exactly where inflammation was found. Then ask what strategies s/he recommends to treat that inflammation.
Your observation about greasy foods is interesting, but probably has much more to do with your current inflamed status than any kind of disease trigger. When your bowels are inflamed it is not fully functional and a lot of foods are challenging.
The SCD (you should do a search for it on this forum) is meant to change the disease process by providing excellent beneficial bacteria and setting up the right environment for those bacteria to continue to thrive. There is a book (of course) that explains all of this.
$125/month for Pentasa is not very much compared to the cost of your hospitalizations if you don't get this disease under control. Biologic meds can also be expensive (more than Pentasa). Steroids are dirt cheap and effective but extremely dangerous for your long term health.