you are, of course, as free as anyone to invent new names or words as needed.

Weightor is not recognised in the dictionaries I consulted, indicating that it doesn't exist as a recognised English word, leaving you with the problem that your English-speaking public probably will have no idea what you mean.

Alternatives might be:

weigher - one who weighs, but this might be limited to real weights and not to judgements, leading me to what I'd suggest:

judge - judge is a term that is not limited to law courts, and, according to your German text, that is what the Gewichter is doing - judging criteria and making decisions based on his judgement.

a)

Siehe Wörterbuch: gewichten

b)

"assessor"?

[I think he's talking about an element of a software which assesses variables to determine a course of action to take. When determining something by looking at variables, these variables are, as far as I know, "aassessed".

Danke soweit.
Die Probleme kenne ich alle ;-)

assessor wäre meine erste Wahl gewesen, gäbe es nicht auch noch den "Evaluator".
Jetzt kommt Ihr. Ich bliebe dann mal bei Weigher, weil vielleicht auch die Frage an sich so künstlich ist, wie Software im allgemeinen.

Mehr als zwei Antworten sagen mir schon mal, dass das Problem echt ist.