Hey @Sinicity!
It is important to keep your goals at the forefront of your mind. It sounds like your goals are:
- Have fun
- Improve Strength and mobility
- Get Faster
With this in mind, here are my thoughts:
To achieve these goals, it is important to steer clear of overtraining. Just because you have the time doesn’t mean that it is optimal to fill all of that time with training. You might consider how you could dedicate your spare time to indirect methods of getting faster. For example, preparing nutritious meals! 
Likewise, make sure to dedicate some of that time to recoup from the added training stimulus you’re putting your body though - this is important in both the short term (inter-week recovery) and mid/longer term (planning entire recovery weeks). I would suggest you take a look at the article below which is super helpful for understanding how your body adapts, when and under what conditions.
It sounds like your body is at its Training Stress Limit. It is a great strength to be able to listen to your body and check your ego.
We don’t want to add Training Stress merely to be training more, especially if our fatigue levels deter us from our primary goal of having fun! I would encourage you to zoom out and view your Training Plan like a game of chess where we are moving pieces to progress the “game” (your fitness) forward subtly and calculatedly. All of the pieces (strength training, bike workouts) have still got to fit on the same board (your training week/ physical capacity), and we don’t want anything slipping off (you becoming overtrained or injured). But we do want to keep moving everything forward. Therefore, we can’t continually push each piece forward. But we can move one piece back slightly to add another stimulus.
With that said, you might find it beneficial to change from a Mid volume Plan to a Low Volume Plan so that you can add in Strength Training without overtraining. This allows you to make progress toward all of your goals 1) Get faster, 2) Get stronger and more mobile 3) Have fun/ avoid burnout.
After incorporating strength training into your schedule for a month or so, then you may wish to re-evaluate your bike training Volume. If you feel like you can increase the Volume at that point, you can do so.
Concerning your strength training timing, I suggest doing what is most practical for you. Consistency is the key to building strength (or any type of fitness). So the most effective plan is the one you can do consistently! 
I hope this helps! Let me know if you have any questions!