They were ready for mass production.
"Ready for mass production" can mean very different things to different people. The broader issue for this is the same as the Wasserfall SAM, which incidentally was a much better system and the reason why Schmetterling was cancelled before the end of the war which is that it's vulnerable to jamming and a very complicated piece of machinery.
The key metric will be it's hit rate 6 months after introduction, after the Allies have had time to come up with countermeasures both technological and training. If it's 100% (essentially impossible with modern technology never mind 1940's) even the Allies can't afford to keep sending bombers above areas protected by SAM's. But more realistically it will have a performance slightly worse than first generation SAM's or in other words 5-10%. So then it becomes a question of production capacity. Is it less than 10% of the total cost of a B-17 (both the plane and the training price of the crew) and more importantly is it enough cheaper than a B-17 that the vastly larger US economy can't sustain attrition against it.
More broadly this is a ground guided system so will have zero impact on the RAF Bomber Offensive so even in the best case scenario it only limits the USAAF's behaviour.
Larger yes, more effective no.
That sounds like wehraboo talk. The Western Allies had a significant technological edge because they had all of their own technical talent plus, thanks to the Nazi's policies, a considerable chunk of German and the German occupied zones technological talent, people like Bohr, Szilard and Teller. That's why the Allies had Colossus, the Cavity Magnetron and Nukes and the Germans didn't even realise they were possible.