Dear Martin,
Regarding your third verse:
nābhuktaṃ kṣīyate karma kalpakoṭiśatair api |
avaśyam eva bhoktavyaṃ kṛtaṃ karma śubhāśubham ||
You are no doubt aware of a similar verse that is found in a number of Buddhist texts. An early source for it has recently been published, from which I here quote it:
na praṇaśyanti karmāṇi kalpakoṭiśatair api |
sāmagrīṃ prāpya kālaṃ ca phalanti khalu dehināṃ ||
This is from the Dhanapālakavaineyasūtra, published in A Unique Collection of Twenty Sūtras in a Sanskrit Manuscript from the Potala, editions and translation by Bhikṣuṇī Vinītā, vol. I,2, p. 692 (Sanskrit Texts from the Tibetan Autonomous Region, no. 7/2. Beijing -- Vienna: China Tibetology Publishing House, Austrian Academy of Sciences Press, 2010).
While this does not answer your question, I thought it worthwhile to cite this recently available old source for the similar Buddhist verse.