I agree with going with the 3x5. Follow it exactly as it's laid out. And, either get more weights or get a gym membership.
12 rep deads won't give you anything but a bad back???

lol! Please. I guess it would all depend on the weight and form you're using. When I do deads I do two working sets. A heavy set of 4-8 reps and a lighter set of 10-12 reps. Last time I did my heavy set of 500 for 8 reps and lighter set of 370 for 12 reps. My back is strong like ox!
Mentzer lifted heavy. So did Yates. The premise of HIT style routines is that you lift heavy...not light.