The problem with the 99 slide limit is because each disc can only hold 99 titles per disc. However, you can have 99 pictures per slideshow so that will increase you slideshow to 99*99 = 9801 pictures.
If you put the 2 slideshows (one of 99 pictures and the 2nd of 34 pictures) and they are subsequent titles, the 99th picture will go straight into the 1st picture of the 2nd slideshow. The only limitation is the audio track does not span multiple titles.
Speaking of audio tracks, to add an audio track to your slideshow, you will see 2 tabs above your filmstrip area. One looks like a camera and the other IMO looks like a bridge over water with a reflection (it's suppsed to be a wave reading on an oscillascope). In any case, the 2nd tab will show you the list of audio tracks that are to be played during your slideshow. To add the audio tracks to your presentation, drag them into the filmstrip area (with either tab showing) and it will add it to your presentation. if you click on the more button after you've added your audio file, there is a box that most user's may find helpful. It will match the slideshow duration to the audio duration so they will end concurrently.
Hope my post is clear enough for you (and others) to follow.