Integrating the products together is something we are moving twords. It is in our plans for future product upgrades.
lets start with one problem first, then move on to the others.
Lets look at using security assist together with Universal Email. You say adding universal email breaks the data assist update. SI would need to look at the code to be sure, but one thing to check first of is the order of the server behaviors and check that only the last server behavior in the list has a redirect applied to it.
If the email code is before the DataAssist code, and the email code is set to redirect after sending the email, the redirect will occur before the update can.
If you cannot spot the problem, send us a copy of the page so we can take a look.
What is the problem you are having trying to use CSS Menu Writer with CSS Sculptor & Site Assist Professional for layout? What specifically is the issue you are experiencing.
We can try to help if you provide us details.
For using CSS Form builder with DataAssist pages, see the "Modifying an existing form with CSS Form Builder" tutorial on the CSS Form builder support page:
I can understand your frustration, we are here to assist you if you run into problems.