This is a known issue that has been addressed in new firmware that is currently in Beta testing.
Correct. SD Card Recordings do not require internet since they are local.
No. This is a known firmware bug that has been fixed. You should see it when the Beta passes QA and is released as a public update.
The green Motion Tagging box is placed there locally by the cam firmware prior to any upload. That is why it is seen recorded on the SD Card when it is enabled. It is a feature you can disable in the settings. It does not require internet.
But, if it was on and did not detect any motion, that may be why there was no upload.
Uploading videos is limited to 5MB files. They are uploaded using the upload button.