Speed is very difficult to increase as we age. Creating speed usually occurs in our youth when we learned to bowl and if we didn't develop a high back swing, it's difficult to develop one now.
Many suggest holding the ball higher in front hoping it will cause a higher arc in back. Because of muscle memory, it usually doesn't work because a person will do things from habit that get in the way of the ball reaching a higher arc.
Another way is to develop quicker feet. This requires more balance and again is more difficult as we age.
Something you can try is to totally relax your arm from the head down. What I'm going to say requires you create a relaxation cascade from your head to your hand at the same time you are taking a little quicker approach.
Relax your lower jaw,
This will relax your neck,
this will relax your shoulder,
This will relax your upper-arm,
This will relax your lower-arm,
This will relax your wrist,
This will relax your hand.
Think of a bull whip. The handle is hardly moving, yet the tip of the whip breaks the sound-barrier. It applies to all sports. Relaxing until our body parts are accelerated by a fulcrum point. In bowling, this is called creating 'leverage'.
If you can increase your foot-work speed safely and stay relaxed, as you begin your slide, your arm will still be high enough that as your slide foot comes to a stop, that leg becomes the fulcrum point for your pendulum swing and you will generate more speed. I've been using this technique for a couple of months now. My ball speed was about 11.3 MPH before and is now between 12.7 and 13.1 now. Just by quickening my feet and relaxing my arm.
I'm 69 and quickening my feet was a little spooky at first, but feels okay now. With time and practice it can be done. How long this will last I don't know. I think as long as I keep my legs strong and my balance in check, it might work for many more years.
You can try and see if it works for you. Just make sure your sliding shoe and the approach is clean every time. Sticking at the foul line with more speed can cause injuries even if you don't fall and much worse if you do fall.
You mentioned throwing lots of Brooklyn strikes. Here's something to consider. A bowling lane is 60 feet long. So small changes at one end can make bigger changes at the other. Everyone loves to miss left and still carry, but we should really stay on our own side. Simply move your starting position left on the approach, 1 board at a time, but keep the same target. See if this doesn't help get your shot back on the right side.
Finally, the position of your fingers has everything to do with the kind of release you will have. If your index and little fingers are spread equidistant from the other 2, this will be your strongest hand position to stay 'behind' the ball. However, you won't get much axis rotation.http://blueprintbowling.com/blog/Posts/axis-rotation-and-axis-tilt-explained.aspxhttps://www.youtube.com/watch?v=b-EHBg3-wn4
If you spread your index finger and close-up your little finger, this will weaken your hand position causing your hand to rotate right to left easier at release and create more axis rotation.
If you close-up both your index and little fingers, this accomplishes the same thing, although it might concentrate more leverage on both fingers at the same time at release.
Bowling balls are usually drilled so that the fingers come out at different times naturally, creating a predictable axis rotation and axis tilt. Changing finger position is another tool to help you fine tune your release for the condition you're bowling on.