This is way out of my experience but can I suggest the following:
1. Look up Kent Petersen (does long-distance ultralight rides on a fixed gear)
2. Look up the Crane brothers' Journey to the Centre of the Earth.

3. Look up ultralight hiking. 50 Lb = 25kg !?!! How can you not decrease that? Are you carrying 10 days worth of food as well as your gear? Maybe ditch the hiking boots for lighter shoes (they only need to last for 2 wks hiking + 2 wks cycling). Look at other camp options. Get an ultralight stove and carry light, dehydrated food. I admire your strength and endurance, but 25kg is just nuts. With respect

4. Look up ultralight bikepacking / ultralight cycle touring / whatever.

5. Ultracycling association website for training plans. Sounds like you are very fit but even so most advise only increasing weekly distances by 10% each week.