What is incumbent upon me if I missed fasting approximately 20 days of Ramadan for various reasons, some legitimate and some due to water from ablution entering (my mouth) or swallowing petroleum jelly, and I am unable to make them up before the arrival of the next Ramadan?

Whatever reaches the throat from the water of ablution or anything else, without intention, does not invalidate the fast. Therefore, you are not required to make up the days on which you did not intentionally break your fast due to water or Vaseline reaching your throat inadvertently. If a fasting person rinses their mouth (madmadah) or nose (istinshaq) and water reaches their throat without intention or exaggeration, then there is nothing against them. The evidence for this is that the Prophet, peace and blessings be upon him, said to Laqit ibn Sabirah: "And gargle deeply when rinsing the nose, unless you are fasting." If a fasting person exaggerates in rinsing their mouth or nose by exceeding three times, or gargles deeply when rinsing the nose, then they have committed something disliked. If water reaches their throat, some scholars are of the opinion that the fast must be made up, while others do not hold that view. If Ramadan comes and you still owe days to make up, you must make them up after Ramadan and feed a poor person for each day due to the delay in making up the fast, unless you were unaware of the prohibition of delaying it, in which case there is no expiation for you. One must be wary of obsessive thoughts (waswas) and turn away from them.