Tim Wakefield maxes out at 70 - 72 mph
Okay, he's a special case and you probably aren't throwing knuckleballs.
re: "forkballs okay?"
--I believe that any pitch type is okay if your mechanics are sound and you are in good pitching condition.
Will the weight exercises you mentioned improve your velocity? I doubt it. Many pitchers don't really realize that about 80% of throwing velocity arises from the core--that is, the primary velocity-generating event is separation of the hips (as they rotate toward the plate) from the shoulders right around foot-strike and a little after...achieving maximum hip/shoulder separation, followed by release of the shoulders as you square up to the plate to release the ball is what you may need to work on.
There are some drills that help with this but, a good pitching coach will tell you to start from the beginning:
1. Optimize your starting position balance and posture
2. Make sure your fanny (actually, your glove-side hip) is moving straight toward the plate at the same time, or even a split second before, your leg lift commences. Generating early and adequate forward momentum is a huge issue for many young pitchers.
3. Your glove-side arm should be in balance with, or "mirror", whatever your throwing arm does from first separation of your hands through to foot-strike.
4. Now you can work on those drills that help maximize hip-shoulder separation at foot-strike.
5. You should stabilize your glove out in front of your torso, over your landing foot--and you should learn to bring your chest forward to meet the glove in your delivery. Guys who loosely flop their glove down to their side before they release the ball are generally not going to go very far in pitching. Guys who pull their glove into the chest can survive longer in the game, but the majority of elite pitchers who really know what they are doing actually stabilize their glove out front and track forward to meet it.
6. Release and follow-through will be fine all by themselves if you master the earlier stages of your delivery.
By the way, an under-appreciated bit of information may help you: Most pitchers have no idea that they cannot throw the ball faster than their body's capacity to decelerate the arm/shoulder after release. Thus, if your decelerator muscle groups--the triceps and the musculature holding your shoulder blades to your back, etc--are not strong enough to decelerate your arm from an 80 mph throw, you will never be able to throw an 80 mph pitch without serious physical damage.
My son and I do lots of prone holds and triceps push-ups to work on these oft-neglected muscle groups.