Hmm...I haven't read the entire story yet and I see that you've bought a new backpack already, but I just have to say that I've had a Fastpack 350 for about 10 years now and it worked really well for me. However the fact that I can't carry a tripod properly made me look at other bags constantly. I normally put the tripod in the side-netting(had to stitch it up several times) and attached a rubber band thingy around the top of the tripod and secured at the top strap of the bag. Where you can hand carry it.

So just a month ago my camera store had a 50% price reduction of the Lowepro Whistler BP 350 AW and I couldn't resist. Glad I ordered it, because frankly I will never want to use the Fastpack 350 again. The Whistler is pretty much the same size, however due to it's internal structure it's practical over the entire size, where the Fastpack slopes towards the top.
My Whistler 350 is not the type II, so it has a ICU. I couldn't really care about it though. I've compared it to the version II and I saw no reason for me to pay more. It's a real sturdy backpack and the ICU gives it even more sturdiness.
My Fastpack is easily folded, the Whistler doesn't fold at all. It gives me lots more confidence.

I never had issues with rain with my Fastpack(I did add a cheap cover for my Iceland tour though), but the Whistler feels and looks way more robust and waterproof. It also is supplied with a rain cover, but I doubt you will really need it if you're not heaving heavy rainfall.

I also like the back access. Instead of only at the bottom of the backpack I now carry my gear directly against my back. It feels lighter doing so, even though the backpack itself is substantially heavier.
The storage compartment is a lot more useful now it covers the entire back area of the backpack. It's also possible to add a little more storage space by opening the zipper that keeps the back smaller when you don;t need the extra space. The storage is also "waterproof" and has a hole at the bottom to let water out. So ideal for hikes and activities in mountainous and wet environments where you might have to pack wet stuff in the backpack. Your gear will stay dry.
Add the ability to attach pretty much anything to the bag with all the attachment straps and loops and you end up with a much more capable backpack.

I like it a lot. In the next few weeks I'll be trying it out in Italy and hopefully I'm still as positive as I am now when I get back