You are supposed to have BGMAIN.EXE and BGMAIN2.EXE in your Baldur's Gate directory. They are part of the game. Don't delete either of them. If you used "Godlike", I think it changed one of them, but that shouldn't cause any problems. (Lots of people have used "Godlike" without any problems; I used to use it myself before TeamBG released their simple, elegant "XP Cap Disabler".)
When I played a game with just my main character and Imoen, they each had about 650,000 experience points when I finished Tales of the Sword Coast. So I estimate that the total amount of experience you can expect to get (divided among your party members) is somewhere around 1.3 million points. A party of six could probably get around 220,000 experience points apiece. I don't remember ever going
way over the limit with a full party of six. However, I wasn't going out of my way to earn as much experience as I could, so it might be possible to earn more experience than that. There are places where monsters respawn, and there are bugs that let you get experience for the same quest over and over (and of course, you can cheat by creating monsters with the CLUAConsole commands), but I never bothered to take advantage of them.
By the way, to answer a previous question, you can use Gatekeeper to change your party members' experience. However, I don't think you can change their level (although I could be wrong), so once they level up, you can't change them back. (That can be a problem if you change your mind and want to dual-class them or something.) There are several things I don't like about Gatekeeper. For example, it doesn't give you as much control as ShadowKeeper (the BG2 editor), and it has a way of doing things it's not supposed to, such as changing a non-gnomish Cleric/Illusionist to a Cleric/Mage if you try to edit the character (since only gnomes can be Cleric/Illusionists, which defeats the purpose of using a character editor). So I tend to use CLUAConsole codes instead of Gatekeeper.
For example, the code
CLUAConsole:SetCurrentXP("161000")
will set the highlighted character's experience to 161,000. Whatever you put inside the quotation marks (for example, 161,000) is a variable, and you can change it to whatever you like. That's true of all of the other CLUAConsole codes, as well.
There are other handy codes such as:
CLUAConsole:AddGold("5000") (substitute any value you prefer for "5000")
CLUAConsole:CreateItem("SCRL75",5) (substitute any item code and quantity)
CLUAConsole:CreateCreature("GHAST") (consult a list of creature codes)
CLUAConsole:MoveToArea("AR3900") (consult a list of areas, or use Ctrl-L to make your own list)
etc.
Use such codes at your own risk.
I also prefer to play in Multiplayer Mode instead of Single-Player Mode. It lets you swap out characters (those you create yourself, that it), and it lets you pause the game and look in your inventory without unpausing the game. The biggest drawback is that you lose your old character's records (such as time spent in party, number of kills, etc.).