Hello Maciej,
I'm afraid what you want to achieve is not possible with the standard Moodle Cloze question type.
1.- In your paragraph (a) I do not understand what you mean by "if there are more right answers than the wrong ones,"
2.- It would be more clear if you used at all times the terms "sub-question" and "question" when talking about a Cloze question type.
3.- (b) That is not possible. The Cloze question simply adds up the individual score of each sub-question, and those individual scores cannot be negative, i.e. can never be less than zero.
4.- "If I change :MCS: to :MRS: above, ..." Using that option does not make sense, since your sub-questions require a unique answer, not multiple answers.
5.- The solution to your problem is probably given in this paragraph of the Cloze question type documentation: https://docs.moodle.org/310/en/Embedded_Answers_(Cloze)_question_type#Using_.22all_or_nothing.22_plugins
I have tried that qbehaviour_adaptiveallnothing plugin and here is the result:
