Those speeds have nothing to do with SpaceX - those are the normal RCI limited speeds on most ships which have completed the upgrade. Expecting more than that will likely lead to disappointment.
RCI has been expanding itineraries for Spectrum and will continue to do so. She has her own schedule for posting new itineraries and things could change.
The Voom package on board is $23-25/day for the Stream tier - about $5/day less on ships which still have Surf. The cost in the planner pre-cruise varies but 10-30% off those prices.
It probably depends on the vehicle but usually on by default- you might be able to disable it. When the vehicle senses you want to go (accelerator action) it disengages.
When you take your foot off the brake the car doesn’t automatically start rolling - a feature invented a long time ago for cars with a manual transmissions to stop you from rolling backwards when on a hill.
Accept the fact that RCI has IT issues and hope it doesn’t happen again. And, yes, cancellations like that have been reported by others. You/TA should have asked for some OBC for the issue and conversion losses.
It probably depends on whether the excursion vendors offer the same thing on the new dates. Any stops which were dropped will have the excursions cancelled.