I checked the JS reference for AI CS4 and could only find the closest thing: Export to Photoshop . With this you could probably run an action or script within Photoshop to convert to Tiff. If you are on some versions of Unix you might use a bash shell to convert to tiff or you could explore a cygwin (Windows) or bash (Mac) terminal script to export to tiff from the generated psd file.
You can't. You will need to use an Action in AI and batch it. Only the options shown in the ExportOptionsJPEG properties are available for scripting. Scripted JPEGs are limited to 72 ppi. They have to be upscaled and then rescaled elsewhere to achieve the ppi you want.