Generally heavy weights are used for building bulk and low weights are used for toning/power. Based on how you want to build strength for your arms and the limitations that you have, I don't think the weights will help you much. You'll want to work on your forearms, triceps, shoulders, and legs the most to generate power.
Forearms - this can be done by curling with your hands the weights that you have. Alternatively if you're willing to spend some time you can easily create your own wrist roller by getting a string strong enough to hold your weights and connecting them to a stick (or something sturdy enough to support the weight). You'll put your arms out straight and curl the weights up and down slowly.
triceps - get 2 chairs that are sturdy enough to support you and do dips. This will also work out your chest and shoulders.
Shoulders - pushups will work best here (also work out arms/chest). You can do different types of pushups for different body parts.
Legs - Squats if you're able to find enough weight to do this activity safely. Otherwise sprinting exercises will strengthen your legs. Many people will forget but your legs are what gives you the majority of your power when you're throwing a ball.
If you have any questions don't hesitate to message me. Also, keep in mind that I've only listed the main body parts you should focus on in order to train for this. You should workout all body parts (especially core).