If I reclass into Infantry, will I still be able to keep my option 40 and student loan repayment?

Your option 40 will likely be dropped if it is in your contract. The reason you got an option 40 contract is because the 75th needs a 25P. If you're not a 25P then that slot opens back up. You might be able to volunteer for RASP from your 11B OSUT, but nothing is guaranteed.

Your student loan repayment plan will likely be partly maintained. If you received extra SRP it is because of the MOS slot you took. If I'm correct, everyone gets 35k, if you got more than that as an incentive that extra is forfeit. You will also forfeit any cash bonus if you are forced to reclass.

I would suggest you pick yourself up and push through the course because you will become a hold while waiting for an 11b slot to open at Benning, and to put it bluntly, you will hate your life while in hold status.

What does your contract say? Look in the 3286-B for your specifics of your contract. You should probably be able to keep your SLRP, that's not usually MOS dependent like a bonus. You have to choose that in lieu of your GI Bill. Option 40 is just a recruiter tool. You can volunteer for Ranger Regiment selection at any time in any MOS. Being "guaranteed" a shot at a selection where 75-90% of people fail and is open to everyone in the Army is a bit like selling ice to Eskimos.

You have to have an MOS before you really are reclassed. If you do not graduate your contracted MOS, Big Army will one for you. This is know as needs of the Army. Good luck and apply yourself in your current course.