If your "standard" chargers work with other compatible devices and as you say that the chargers all feel loose when plugged into the tablet, then it seems as though the port may have become disconnected from the systemboard, That is perhaps why it is not charging.
A lot of USB ports in tablets are directly mounted onto the systemboard, i.e not connected by a flex cable plug connection but soldered onto the board.
The tablet would have to be opened to verify this and if the USB port has come loose the it will need to be soldered back into place.
To do this you will need the appropriate skills and tools to perform surface mount soldering.
If this seems too daunting, then I recommend that you contact 3 reputable, professional, electronics repair / mobile phone repair services and ask for a quote to repair the port. I suggest 3 as this way if their quotes are near each other as regard to the estimated cost of repair, it gives a better idea of the real cost of the repair.