Welcome to the forum Supreme!
After only 4 days, I doubt any amount of microbial activity could cause gas production in your cheese assuming you had adequate sanitation during your make, especially if there is no swelling.
As for the curds prior to pressing, I don't know that they can be over-stirred, but over-cooking them (at too high of a temperature, or too long) could have caused excessive whey to be expelled, leaving them slightly harder and drier than desired, making them harder to meld together in the press (hence the openings). Pressing with a little more pressure may have closed this cheese up a little better, but would have made it a little more different from the cheese you intended to make.
All in all, if you're satisfied with the taste and texture of the cheese, then I'd say you did a good job and congratulations!
If you're not satisfied, I'd still say good job, you only have a few minor tweaks to make, and you're well on your way to perfecting your cheeses.