Hello jknise,
From your description I would suggest that you look in to a product called [color=orange]Quest3D. [/color]
Although it is not [color=orange]VRML compliant, in my view this is possibly the most appropriate engine for what you need to do. [/color]
Quest3D is extremely fast, it can handle huge worlds, and since V3.0 got most if not all the latest goodies from DirectX 9.0c. 
Most importantly with its unique graphical interface and templates system it allows designers/developers to create advanced real-time 3D productions (simulation, architecture, landscape visualization, business presentation, virtual-reality training, product visualization and games) without the need for programming or scripting.
Also, development is always in real-time no need for compilation or Run the project each time you want to test what you have done. You work directly on the end result.
Regarding your most needed features:
1 Quest3D comes with an Autocad exporter to the X file Format as well as other for MAX or Maya and Polytrans.
2- No programming/scripting languages to learn, only a graph editor where you link blocks (called Channels) together to create logic. A lot of the simplest logic like walkthroughs and different type of cameras are already available under the form of templates.
3- Yep huge project, but in my view not too huge.
The [color=orange]biggest project I have seen made with Quest3D (by a Dutch company called 3idee) is a 3 x 3 miles environment boasting 6.5 millions polygons. obviously these are not handle altogether in one go by the engine and your project will probably need to use concepts such as portals and/or LOD etc
Although Quest3D do not come with a portal by default - a user has actually developed one - It can be done. 
A few examples of smaller projects made by users here
4- In Quest3D you can launch any external application directly from inside your project, you can open an URL and you can even use avi files as moving texture.[/color]
5- [color=orange]Costs starts at $[color=white]157.00 [/color]with the Lite Edition. An Educational Edition is also available (restriction applies). [/color]
Anyhow, most important of all in my view, is that there is a very transparent licensing model with no royalties and no hidden extra costs. In short, cost is limited to the price of the Edition(s) you have decided to purchase. Nothing more:bounce:
I have also a few other posts about this great product you might find interesting:
[color=orange]http://www.cgtalk.com/showthread.php?p=2330864#post2330864
http://www.cgtalk.com/showthread.php?p=2294556#post2294556
http://www.cgtalk.com/showthread.php?t=239862
http://www.cgtalk.com/showthread.php?t=224098
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You want to give it a go? then just download the [color=orange]Demo Edition (Save disabled).[/color]
After toying with it a bit, if you need to push your investigation further, just [color=orange]let me know as I will provide you with a free Trial Edition Key giving you access to all Quest3D features inclusive of Save and Publish for 30 days.[/color]
Anyhow If you need more info or get stuck with something, please do not hesitate to ask here or to PM me.
Hope this help a bit!!
