To be honest, given your length of time training, I wouldn't practice things like san shin, kihon happo, or specific 'kamae' too much.
You're likely to solidify bad habits without some occasional 'course correction' by your instructor.
I would work on two things mainly:
- Flexibility: Strech every day.
- Ukemi: Roll, a lot.
If your ukemi is incorrect the ground will fix it - so it's very easy to make sure you don't go off course. The flexibility will help with this.
In my opinion, the way to get the best the fastest is to have excellent ukemi. If your ukemi is good you'll be able to receive and learn from class instruction without worrying about your safety.
You could practice all that other stuff, you may be doing it right, you may be doing it wrong - you'll probably end up about where you left off.
If you go back with ridiculously good ukemi you'll gain enough sensitivity to feel and understand what the instructor (and other skilled practitioners) are doing. Also people will be more inclined to train with someone who can clearly be responsible for their own safety, leading to greater training opportunities with skilled people.
Be sure to experiment and roll all different ways with both hands, one hand, no hands, shoelaces tied together, brace on the knee so it can't be bent, blind folded, one hand tied to your foot, etc...Anything and everything you can think of. 'Real' ukemi never looks like the 'basic' versions, and a habit to execute a 'perfect' roll can cause injury if your arm happens to be locked up in some strange way or if you're near a cliff.
Also, it's completely do-able. A few months of regular focused ukemi training is enough to improve a beginner past the level of most people who have been training for years in an unfocused way.
