About certain foods AND WEIGHT GAIN, LOSS, OR MAINTNENCE?

As long as you don't have any other health issues, protein and carbs are better for you than sugar or fat, at least in excess. I'd increase both, but go heavier on the protein than the carbs. So, I'd eat the ice cream or the pudding but not too much of either. The boost is probably fine, as is any other meal supplement that you like the taste of. Some protein shakes taste pretty good. The chocolate milk probably has a lot of sugar in it, so I'd be careful about that. And I'd go right ahead and exercise, but concentrate on building muscle (which is heavy and can be bulky) rather than burning calories.