The dimensions you stated are quite good. I'll give you a few examples (using "Frankford Arsenal": digital calipers):
Picks
Peterson slim gem: 3.9 mm (taking into account full hook with diamond)
.37 mm width
Southord (hook-standard) 3.08 mm (hook included)
.50 width
Peterson hook with diamond: 3.85
.62 width
Navigator by "Dino" small hook (great for locks like Schlage deadbolts): 1.99 mm
.57 mm width
(Please note that the shafts are considerably smaller than the overall heights)
It seems like you have enough material. A few problems to consider:
1. You probably want a handle
2. The steel sounds flexible, but, watch your bends for tension wrenches, sometimes it snaps, i.e. 45 degrees plus
3. Most picks will be at least half the width of your material; you will need to thin it evenly and consistently.
4. With a dremmel you could make a pick in a couple minutes, by hand, figure on awhile longer-although to me that is half the fun
*all of this assumes that your steel is o.k. for picks and wrenches. The best way to find out is to make some, search, you'll find plenty of templates.
Post us a pick when you’re done
Dunno what I was thinkin...