I've done two rolls of 5245 in C41 and my conclusion is that remjet should be removed before processing. I do not have any scans but looking at the negs I see some marks witch simply do not happen when processing a C41 neg. They are somewhat similiar to yours.

I suppose the developer is alkaline enough to make remjet soft so some particles can get into emusion. However someone here on apug reported removing it at the end of process with no problems. It might depend on something hard to account for with anecdotal experience we have - agitation, age of film etc.

Cine labs here do process 135 rolls in ECN so I do not bother to scrape the horrible remjet myself.

As for contrast, skipping the bleach might increase it to that of C41 neg or somewhat higher. It works well with ECN bleach bypass but straight C41 gives somewhat higher contrast than ECN so C41-BB might be too drastic. On the other hand extending development time might work. Anyway contrast is moot if you do not intend to print optically.