after you beat the main story are there any enemies left to kill?
is there stuff left to do or does it show the credits and then start you over at the endar spire?
is there any way to change and manilpulate your "light/dark side meter" after the game is up and there is no missions to do ?

To The First Question - No, There Shouldn't Be Any Enemies Left If You Have Gone Everywhere And Done Everything Including The Main Quests And The Side Quests. There Are However Some Enemies That Do Respawn But These Are Few And Far Between And They Don't Really Give That Much Experience Anyway.
To The Second Question - No There Shouldn't Be Anything Left To Do Once You Reach The Star Forge (Except The Starforge Itself LOL) And Even If There Is You Won't Be Able To Leave The Star Forge And Travel To The Other Planets Once You Are There So Do Every Thing You Need To Do Before Traveling To The Unknown World And The Star Forge. And Yes Thats Pretty Much What Happens After You Defeat Darth Malak...A Final Cutscene And Then The Credits. You Can Always Make A Save Game On The Final Level Of The Star Forge So You Can Load It And Fight Malak Whenever You Want Which Is Fun Too.
And The Answer To Your Third Question Is No There Isn't Anyway To Make A Significant Change To Your Alignment Once You Reach The Star Forge. You Could Change Your Alignment To Dark Side Or Light Side By Cheating However. Just Hit The "~" Button On Your Keyboard And Type Either addlightside For Maximum Light Side Points Or adddarkside For Maximum Dark Side Points. Other Than That If You Extremely Love This Game As Much As I Do Your Just Gonna Have To Restart And Play It All Over Again! Maybe Next Time You Could Be The Opposite Of What you Were This Time Or You Could Be The Same Thing Its Totally Up To You. Trust Me If Its Your First Time Beating The Game You Should Definitely Get A Walkthrough And Go Back And Do Every Thing You Can Possibly Do And Do Whatever You Might Have Missed And Take The Time To Watch All Of The Cutscenes And Listen To What Every Character Has To Say. Sometimes Theres More To The Game Than Just The Game.

thanks =]

No Problem.