I will offer some advice from my experiences. I have previously developed applications and site using Dreamweaver and specifically ADDT, which is now discontinued. If I where you I would look at a PHP framework, they are designed for rapid development and are generally well supported by their respective communities.
I would take a look at Codeigniter (it's free), offers a wealth of features, has good security and a reasonably gentle learning curve. There are loads of tutorials and support from the community is first rate.
You can continue to use Dreamweaver CS5 for the design and with new PHP features it can also be used for development. I know your problem there are so many options it can be difficult to go down one route without closng another, in the past 3 months I have concentrated on PHP, Codeigniter and jQuery with these three I feel now I can do anything.
@trangman63 - I usually get copied on posts to this form but for some reason they are taking for-ever to get to me if at all.
I have been a longtime user of Dw (since UD4) in fact and a long time user of ADDT and the previous incarnation that was originally created by those great folks at Interakt.
For several years I built solutions on ADDT and the previous Interakt product and was a strong Dw supported and advocate. I had over time been able to build an excellecnt comprehensive CMS based on ADDT which suited my target market.
When the hammer dropped on ADDT I was very concerned about which way to go. I decided to never be dependent on Adobe again and looked for alternatives. Firstly, let me say that I dont believe that WordPress and Joomla are options for my target market. WordPress has a complex User interface and whilst it is an excellent Blogging system, it really is inappropriate for a general purpose CMS for site owners with limited knowledge on how a website works. As for Joomla - it has an overly complex User interface and I would never impose that on my clients.
So, what to do ? Initially I noticed that one subscriber to this forum had decided to go with CakePHP which is a very attrctive option if you have the time to search for a CMS that is based on that framework and would be suitable for your needs. This developer, fortunately for him, had the skills to put CakePHP to work for his needs. But, I had relied on ADDT for too long and had not gained any new skills apart from all the ins-and-outs of ADDT.
Then, sometime later, another subscriber offered his advice concerning codeigniter another PHP framework similar to CakePHP. Initially I considered that the learning curve was too steep to be able to develop my own CMS based on codeigniter so I looked at a few of the CMS projects. Eventually, I cam across PyroCMS.
I fully recommend to any ADDT user that found themselves stuck without ADDT to drop Dw and take along hard look at pyrocms.com.