What say you? Will i be OK? Should i just nut up and buy a good seat bag? Or should i just quit over-analyzing everything and go ride my bike in the woods?
Go hit your local trails for a couple-few hours ride and see what you think. Sure, other riders will think you're a nut, but...welcome to the club! If the setup needs modification, better to find out now then to be miserable and trying to figure out how to change it on a long trip.
I really don't like having much real weight on the bars either. Too poor of handling in my opinion. I've been riding with nothing attached up front, but will be experimenting with putting my sleeping pad on the handlebars this season. Very small packed size and will only be about 1lb 3oz total.
I'd be more worried about the backpack weight though. Not so much back issues for me, but the added weight (and riding hours) puts a hurt on the sensitive areas down below.
If you need one, you don't necessarily have to shell out the bucks on a seat pack. You can make a cheap and effective seat pack from a stuff sack and velcro straps. That's my setup.