I don't enter any information into the Tooltip or Custom Screen reader text windows unless the fields caption isn't explanitory enough to convey what is supposed to be entered into the field. Then I use the Custom Reader Text window because by default CustomText is what's showing. I noticed that with Tool tip it did seem to be reading the label and then what I had typed in so it was basically reading it twice when I saved the form as a static pdf. When I save it as a dynamic pdf and have text in the accessibility window under the Custom Reader text, it does not read the caption showing on screen, only what I have typed into the custom text box.
And as far as checking the next box and not the one you have selected, I can't help you there. I made a little sample with 3 checkboxes and that's what I ran a test on. It seemed to always open reading the last checkbox first when I was using JAWS to listen to the form. I had to tab to get up to the first checkbox. And on the static pdf it read the label and then the custom text. On the dynamic, it only read the custom text. But the dynamic caused JAWS to start babbling the first time I opened it. When I closed it and reopened, no babbling.
I know this probably won't help you Norbert, but I did learn something in the process. JAWS doesn't like to type on this forum.