1. For more current, you should probably use more 2N3055s (or better yet, a modern transistor) in parallel. There are also darlingtons in that current range, which saves the trouble of the 2N4401, but meh.
2. For accurate current limits -- no. It's simply not the right circuit for that.
For that, you need to change the circuit by adding a current sense path, and an error amplifier. The outputs of the two error amplifiers need to be reconciled (i.e., wired-OR), and the result applied to the follower.
When op-amps are wired-OR with diodes, one saturates to the opposite rail while the other does operation. This causes
integrator wind-up, i.e., it takes a dozen microseconds for the saturated amp's output to rise back up to operating level. In that time, the output over/undershoots. It's a high-level version of diode recovery: instead of current overshooting due to semiconductor physics, it's current overshooting due to delays in the control system. The overall effect is much the same, though!
You need to use a wired-OR configuration that prevents windup, like this:
https://www.seventransistorlabs.com/Images/Limiter2.png a discrete op-amp wrapped around the one error amp, so that the error amp is always in control, but its inputs are manipulated to perform one duty or the other. Note that this circuit doesn't have amazing gain on the limiter loop (too much gain there, and you have the same problem as always: oscillation), which also gives it a somewhat soft threshold, and less precision within that limit. Still, it's much better than a single Vbe.
It's also worth noting, your circuit is drawn as almost DC-only. That is, no consideration has been made for AC characteristics, aside from the rectifier. This may be a matter of representation -- that it's not a practical circuit, and "details are left to the student", so to speak.
But if it's not being represented in that way, then it is disingenuous, and those details should be added.
To that end:
- There should be some compensation across the amplifier (OUT to -IN)
- The output should not be overdriven (add series, maybe 1kohm, from OUT to 2N4401-B)
- The current limiting transistor should, itself, have a current limiting resistor in series with its base, maybe 1k; this prevents damage under sudden load conditions
Tim