How to allocate my time for two subjects?
You just have 6 months for this current job. Your personal interest can stay with you forever, and you can invest more on that when you have joined the grad school. 

For now, I would recommend giving your 100% to the current research and get more productive outcomes on this, with good papers and collaborations. If you feel like you have too much time, energy, and enthusiasm, give 200% of it to your current work!