Do a ton of practice questions and learn off of the ones you got right and wrong as you go through them.
3 hour blocks ---> 45min sections.
Try to do 4-6hrs a day. 2 hrs minimum on top of school/work/whatever you have going on right now.
Subject planning does not matter as long as you hit 2-3 subjects a day for solid 45min sections for each.
Do not get fixated on 1 subject the entire day.
Focus on your weak subjects, not just your strong subjects.
I gave myself 2.5 months for the OAT and planning to take it on July 14th. I think it's good to set a date so you have a goal in mind to keep you on track and prevent procrastination. I think most people give themselves roughly ~3 months on here for the OAT