I still have the problem of my models, and level files
I really can't think of anything other then going for custom binary format file. I think its well worth the trouble of implementing it though. I was using .dae(collada) models before, it was taking anywhere around 30 second to 1 minute depeding how many models to read. After implementing a CBF it took around 5 seconds to load all models. So my advice would be none other then CBF.