If you go to the disABILITIES FAQs thread, and look at the post about wheelchairs/
ECVs on buses, there ae several links to past threads. Some of them are discussing just what you are asking about.
Because a guest's
ECV had tipped over backwards while driving up a ramp, Disney changed their policy to require ALL wheelchair and ECV users to board by backing onto the buses (from what I had heard anyway), without an understanding of
different types of ECVs/wheelchairs and why that was not appropriate for all.
Most ECVs are heavy on the back and very light on the front and are prone to tipping over backwards. This is a known problem - a similar situation has caused many farm accidents to occur when tractors go up ramps to get into barns, etc.
Some ECVs (like yours) and most power wheelchairs are not like that and their weight is more distributed. Backing up with those types can be dangerous or impossible. A number of people on the DIS Boards (plus, I don't know how many people outside the DIS) worked with Disney to get the policy changed. Some of the "work" was writing letters/emails to Disney. Some was providing information to sympathetic bus drivers.
The policy was changed (I think about a year ago) to reflect the guest being able to detemine if backing up is safe for them.
Some of the people who had problems in the past and are still active on this board will hopefully come along with information for you.
My DD doesn't take her power wheelchair to WDW (yet), so we have lots of experience with manual wheelchairs and buses, but none with power. I was one of the "experts" who provided information about mechanics/physics/how wheelchairs/ECVs work for the drivers.
Hopefully, you will get some replies to both of your questions. You may want to make a separate thread with the cruise questions. I know people have posted about using an ECV on cruises before, but some of them might not look in this thread.
Let us know how things worked when you get back.