mamabee,
1) For the slippery elm bark powder, I would recommend your getting it from:
http://www.pacificbotanicals.com/store/product.php?productid=327
That's where I get mine, as it's organic and pretty cheap too. IMO, You should be taking 1 tablespoon mixed in a little water - which will become gel-like, drink it down before it gets too thick - 3 times per day.
2) For the psyllium seed husk powder - I see that pacific botanicals has it there as well (organic):
http://www.pacificbotanicals.com/store/product.php?productid=593
3) For the VSL#3, if you have good health insurance, I would recommend you get your GI to prescribe for you the VSL#3 DS (IMO, to be taken 3 times daily), and you might only have a small copay.
Do you have good coverage that would pay for it?
4) Regarding the Vit. D - you need to make sure you have been blood tested to see if you are low in it first before taking it, as there could be toxicity issues otherwise. Have you been blood tested?
5) With regard to foods, I commend you on doing the SCD diet. I know it's tough.
I just want to make you aware of one more thing: food combining. If you mis-combine foods, it can wreak havoc on your gut with gas, distension, bloating, pain, cramping, and D. Here's a good informational link which explains it well:
http://cureforulcerativecolitis.com/step-1-methodology-to-eating
I would suggest you start with VSL, then slippery elm, then psyllium.
Let us know how you progress.