ASAP_03 Chrysler T&C w/EMC Gold Hand (Handicap) Controls - Fluttering Speedometer?!

Hello

I have muscular dystrophy and drive my own vehicle. I am writing because I am having issues with my van.

For the past year the battery has gone dead in less than a week, and now goes dead within a couple of days. I diligently jumped it then replaced the battery. I also have been having an issue while idle or when stopped (but not in park, only happens in neutral, drive, and reverse) where my speedometer will jump to 20 mph and flutter up and down. In this process when it first starting to flutter the car kind of makes a sound similar to thunk thunk (this is really hard to communicate in writing) and feels like something is happening but I cannot describe it and it does not happen all the time. When accelerating it will return to zero then accelerate normally when pressing the gas. I do have a video of this happening and attached it to this Discussion (I think). Sometimes the check engine light comes on but sometimes it does not. I had my mechanic look at it and he thought it is the transmission, after swapping the speedometer sensor, and, referred me to a shop to have it re-built. He cleared the engine codes to see if it came back and the engine light has not but it still flutters (the video was taken after the check engine light was reset and it did not come on).

I am looking for any and all input before I act on such an extensive and expensive fix (being disabled I really do not have the money to be wrong). With the power issues I am not confident it is the transmission and was wondering if it could be low voltage or something else (I pray)? Please let me if the video did not attach. Go Red wings & Thank you for any help!