There is a tool called Universal Minecraft Editor which is capable of reading and modifying chunk data of a world. You can download it here: https://www.universalminecrafteditor.com
when you open it, it will ask you to choose a platform so choose Win10 (not sure if Bedrock edition is considered Win10 or Pocket Edition so experiment with that).
The next screen will allow you to choose a save file so do that and click open. Once the save is open, click on "chunk locator" button on the sidebar and find the area with the command block. Click on the chunk which contains the command block and click "open". A new window will pop up with with a hierarchy view and a branch called Level or something simillar. Expand the level branch, expand "Tile Entities" and you should now see all the tile entities including the command block itself. Simply remove the command by double-clicking on the command field.
The same goes for the entities. Click on the chunk with the entities, click open, expand Level, expand entities and delete them.
Once you're done, click the three dots on the top right and click save all.
If you don't know how to do it, I'd be happy to help with that. Good luck!