Hi rose, welcome to the SAF forums and thanks for your interest to Serve your Country.
1st Question: Why wait a year to apply? Why not try in the fall? The more chances you give yourself, the better of a chance you have of receiving a scholarship. (You have a 0% chance of getting a scholarship if you don't apply). Now, I understand that you are worried about your academics (I'm assuming you are referring to GPA), but if you show up in the fall and really bust your butt (academically and physically) and really show your drive and passion, that should give you a pretty good chance at getting a scholarship. It also shows that you have taken the initiative and that you have courage (I know there's a better word than that, but I cannot think of that world for the life of me) - key parts of being a leader, be it in the Army or civilian world.
Although it's hard to say how likely is to get a scholarship, since all schools handle that process differently.
2nd Question: A common misconception that many students get is that scholarships can increase chances of getting active duty. Which is perfectly fine! That's why you came here - to seek out that source of knowledge! Unfortunately as much as we'd like that to be true, it is completely false. What happens is come fall of your senior year all of your info will be placed into a package, to yield you your Order of Merit Score - which is tied to your placement in the Order of Merit List. What does this package entail you ask? Well as of now your CGPA (40% of the package), your physical fitness test score, commander's letter of recommendation, land navigation, clubs/extracurricular activity involvement, and many other tiny little things that I don't want to bore you with.
In short, it's basically like in high school how you have a class rank; just think class rank = Order of Merit List. The only difference is the Order of Merit List (OML) is nationally ranked, so you will not just be competing against your fellow cadets at the Army program you are participating in.
So what the OML amounts to is the deciding process on what job you will get, which component in the Army you will serve (Active Duty, Reserve, National Guard), and even base location. And as you can imagine, the higher up you are on OML, the better chance you get of getting the job you want, and in your specific case - Active Duty.
Now granted there are exceptions to how this all works, but this is just to illustrate the important parts.
Your best bet to have all of your answers directly answered, would be to call up the Army program at the school you are transferring to. Also, just a heads up - do not be discouraged if you cannot get a hold of someone immediately. During the summer a lot of the cadre (ROTC instructors) are out of the office for summer training, LDAC etc. So what ends up happening is, the program gets run on skeleton crews over the summer. So just keep trying - and if not, try emailing them too.
Best of Luck.