I think 150 - 200 ‘fairly hard but certainly not full power’ jelqs is a good general number, but numbers are not important. How your unit feels is the important thing. Try to learn to feel when you have done enough, because your erection quality and grip strength will change session to session. When your dick says it’s had enough, then you have finished.
Kegels and jelqing will certainly keep your dick healthy; whether it would be as good as it could be without the drugs only you can tell. Because they have the benefits of helping control orgasm and potentially giving you a bigger unit, you are going to do them whether they give you a rock hard unit or just improve it.
However, the best route to a (natural) rock hard penis is aerobic exercise. Really it is. :)
Clamping does nothing to stop length growth. Some believe it is harder to gain length if you gain more girth because their is more tunica to stretch. To a very small degree this may be correct, but for size (cu. in.), girth is far more important than length. I think it is best to work on both together.