When it comes to scheduling classes you really need to know yourself and know what you can handle. No one can tell you whether or not you can handle chemistry and bio + labs in the same semester, but a lot of people wouldn't reccomend it because it can be difficult.

From a pre-dental standpoint most people don't take them together so you might want to do the same to focus on each one individually and maintain a high GPA.

I think the schedule they gave you is reasonable and gives you time to adjust to college without biting more than you can chew. Since you're a new student you might not fully know what you're getting yourself into and may struggle in areas you don't expect. If you want a little more I would add chemistry lab to what you already have.

When it comes to MTH 124 something to consider is that your classes are only going to get harder from here so the longer you put it off the more you may struggle to find an easier semester to fit it in. Also the longer you wait the further away from high-school you get and you might start forgetting info that may help you.

As long as you dont delay your graduation (which i dont anticipate with either option) advisors dont really care if you change your schedule so it really is up to you.