1. When filtering "Text1" it will show every value in the Data source, even though Type was filtered (GAMEIN):
See the Small inverted triangle on side of your filter. Check ONLY RELEVANT VALUES instead of All values in database. That would resolve first issue.
2. Can I change the "Text1 (Copy)" label in the column header?
Right Click and Rename this Field under Measures. Give it any name of your choice.
3. Most importantly, do you think this data design can be explored to Tableau full potential?
Yes, you can use this data for any insight you need.
Hope it Helps!!!