Spoke tension - is a left tilt ok to prevent explosion? The left hand steel blade spokes of my WH-RS30 (not 30A) are constantly exploding inside of the nipples when going up hill in a standing position. I have increased the right hand side tension to about 2150N (1600N is the recommended limit for the rims) and the left hand side to about 1150N (1100N recommended limit). The wheel now however is not perfectly centered, but slightly shifted towards the left. Is that acceptable? 

I don't want to tighten the right side any further, but lower tension on the left is not acceptable either. I only increased the tension by about a 1/4 turn.

Is going that much above rim recommendations dangerous? No right hand spoke ever exploded, only the left hand side. Might I just be to heavy / "strong" with 90kg?

Maybe my TM-1 (tensiometer) is a bit off? The left side spokes still feel awfully easy turnable. What settings do you use on your TM-1. Mine are 20 right - 15 left because I think the spoke is closed to a steel blade with 1.0mm x 2.2mm

Interestingly, as I ordered repair spokes, they came with longer nipples (part number didn't change). Is this a sign of a known problem?
Your wheel is overtensioned. That is not good as it will eventually lead to premature failure somewhere, maybe worse than you're currently experiencing.
In the case of wheels that don't come as manufacturers' sets, ie the spokes, hubs, and rims were all purchased separately, the spoke and the rim and even the hub are going to have different maximum tensions. In this case if you overtension the rim it will either not stay true or crack at the spoke holes- in extreme cases it can even encourage the wheel to taco under less lateral load. If the spokes are overtensioned they will eventually snap. Should the hub have the lowest maximum tension and you overtension it you run the risk of breaking the hub flange.
In the case where the wheel comes as a manufacturer's set (for example, many high end Mavic and Shimano wheelsets have compoenents that are all proprietary and only work with a given wheelset), you're going to have a maximum tension which is still going to be limited by one of the aforementioned components but you likely wont know which one. Same rules apply though- something will prematurely fail if you keep the wheel overtensioned.  
You need to let the tension down instead of bringing it up to get the dish correct. How old are your wheels? If they're relatively new you may have a warranty issue on your hand, although you may have voided said warranty by overtensioning the wheel. If the wheels are old, it's important that spokes have a fatigue life just like everything else and you may be hitting it. Often when you get close to the fatigue life of the spokes on your wheel you'll bust one after another until you relace the wheel.