also, when you do go for a free weight barbell squat you'll find that as long as the bar travels straight up and down there's a very good chance your back does lean forward a bit, this is normal physiology and perfectly acceptable form. Your back roaching in the middle is NOT acceptable form.
I cant recommend a book called "starting strength" enough
bending your back for deads tells me you have too much weight on there and Im guessing for both your back strength and hip abductor strength are the missing links here
go for t-bar bars, bent over barbell rows, cable rows and some pull ups..even if theyre assisted
for hip abductors, cable abductions and the hip abductor machines and well as walking sideways and backwards on a treadmill
a lot of people nail form on a smith but if you were my workout partner I'd have you start on a bare bar and keep adding five lbs until we got into an issue then I'd back it off a bit and call that your working weight, slowly adding 5 lbs a week to that