Many years back I developed a major project using Flex. I devoted several hundreds of hours to the project before I proved that the Flex output did not work as I expected.
I accept that my expectations were probably unrealistic, but I learned some important things about Flex -- much like you are learning now.
Someone will probably correct me on this, but I believe that many of the restrictions that you are encountering are related to the underlying properties and restrictions of the .swf files which Opus produces via Flex. Where this is the case, DW can probably do little if anything to remedy the issues you have listed recently. So, please don't be disappointed if DW cannot grant all your wishes.
When I first encountered Flex (it was then an optional add-on that we purchased) I thought it opened up possibilities for my project development. I'm sure there are Opus users who find Flex is perfect for their needs, but in the intervening 6 years, I continue to categorise Flex as something that
seemed like a good idea at the time.