I would like 2000AD to be TL 10. Going down from there is pretty easy. WW1 and WW2 had sufficiently different technologies built during them that they were very different wars. The period between Civil War and WW1 saw a lot of rapid advances too; just about every ship built was obsolete by the time the keel hit the water. Iron plating, breech loading, coal power, oil power, guns growing from 10cm to 40 cm or more... lots more changes than can be easily listed.
The differences between Napoleonic Era and Civil War, just in infantry weapons is pretty big. Cavalry went from dominating the battlefield to being a simple joke in the space of a couple decades, due to rifles being a lot more accurate.
In the list above, regarding the seperation by ages, you forgot the Information Age, a very crucial time. In fact, the spread of information has allowed tech to make large jumps.
Discovering how to read and write made it possible to pass information down in some way besides rote. The printing press made it possible to mass-produce information, so that everyone could have access to it relatively cheaply. Steam power allowed the information to travel very rapidly. News could reach the entire planet within a few days of it happening. Computers have allowed information to spread instantly, in addition to being able to process larger and larger amounts of it on a faster and faster basis. Today, we have too much information, and computers are required to distill it down to what we are looking for.
In the future, nuclear propulsion systems will allow us to reach other planets in our system. Higher tech versions will allow us to go faster, and perhaps reach the nearest stars, much like the explorations in the 1500's were. A faster-than-light drive would allow us to regularly travel and communicate with those other stars.
So you see two important functions of our growth. Information and speed of travel. Another is energy production, but I think you guys don't need me to spell that out. If you define your tech tree in terms of these three things (and maybe there's others), then you will see where the real boundaries lie.