Issue 1: PowerApps uses the 'internal' column names of SharePoint, I guess you might have created the column and renamed if after that. At the moment of creation, SharePoint gave it an internal name, that's why you are experiencing that. To solve this, you will need to create a new column with the name that you want, and replace tje Field1 column with the new one.
Issue 2: This has been reported already on the forum, and Microsoft are working on a fix. To resolve this issue now, delete your data souce and add it again (note this should not impact any of your formulae)
Issue 3: Not sure, maybe it would be OK after you resolve issue 2.