Diego's Rescue Pack

This Rescue Pack cake is covered in fondant with fondant details (and royal icing filling in all the cracks). It was actually carved from 6 vertically stacked layers of cake. It was supposed to be standing up but the weight of the fondant started making the cake lean over. So I just laid it down on its back. This was my second time using fondant and I pretty much had the same problem as my first time - fondant making the cake cave in and tearing. Any suggestions on how I may improve are very welcome!