If Asacol doesn't work, then you can switch immediately to Pentasa, because they are basically the same med, but released in different areas. Then you can see whether the Pentasa helps you, or not.
If it doesn't, then you might try Entocort. Yes, it's a corticosteroid like pred, but far less likely to cause serious side effects, because most of the med stays within the terminal ileum, instead of going thru the entire body.
There's no point in taking Pentasa with Entocort. Pentasa is not that effective for most Crohn's patients and certainly unlikely to help Entocort. Entocort will either work or not, on its own...it might take a few weeks for it to fully kick in.
Try doing one med at a time...otherwise, you will find it hard to figure out which med is working.