Source: p 174, The Catholic Christian Instructed in the Sacraments ..., by Richard Challoner, 1786
A. Continency is not required of all, but such as have by vow engaged to keep it: and therefore, before a person engages himself by vow, he ought certainly to examine whether he has a call from God, and whether he can go through with what he thinks of undertaking : but after he has once engaged himself by vow, he is not now at liberty to go back: but may assure himself, that the gift of continence will not be denied him, so that he uses proper means to obtain and preserve it, particularly prayer and mortification, which, ♦ because Luther laid aside, by quitting his canonical hours of prayer and other religious exercises, to which he had been accustomed in his convent, no wonder if he had lost the gift of continency, which he owns he enjoyed whilst he was a popish friar.
I guess the bolded which as a relative pronoun, but despite numerous rereads, I'm lost and can't anatomise/parse the phrases after the lozenge (♦ )? Please show the steps and thought processes? This quote exemplifies my persistent scourge; I can't even determine which is the right syntax here:
1. {Relative Pronoun or Adverb} + Subject + Verb or 2. {Relative Pronoun as Subject} + Verb