I slouch alot myself as im behind a monitor myself. Try and sit up straight if you can! Then again im not one to give posture advice as im often putting my feet on something and sitting the most pecurious positions (BUT SIT UP STRAIGHT
)
With regards to the routine (more importantly), I recently came off it for the 2nd time, often I like to get off splits to shock my body into something different. The routine does work but you may find you want to tweak it as it is rather boring doing the same things day in day out.
i.e. switch lat pulls downs to t-bars rows.
Id never do the same exericse for a muscle group 3 times in a row. Say for chest, one day id do flat, one day incline and 3rd decline...... see where im going?????
So it might be worth tweaking it around to suit you, go on the routine for 6 weeks and see how you fair on it. After that you can go bkac on splits!
With regards to back, perhaps a split is more suggestable for you.
My routine is as follows for back exercises (it might be a bit much for you though)
Deadlifts
t-Bar rows
Dumbbell rows
Chins
Latpull downs, (2 front, 2 back and 2 mid)
set and reps are to suit me on the day (i dont stick to one thing)
but i often will do a different exercise if im feeling adventerous or bored etc...
Wanna keep the muscles guessing and that above hits the back very well!
You may wanna focus how your doing your rear delt work, are you doing them???