Do feelings of gloom, anxiety, and obsessive thoughts regarding the unavailability of marriage contradict supplication, and are they a sign of its non-acceptance or of God's wrath? Is it forbidden to think about this matter excessively?

Whispers and emotions do not contradict supplication; rather, continue in it, as it is one of the best means to achieve what is desired. What you mentioned does not indicate Allah's wrath; rather, it might be a trial that elevates ranks and expiates sins through patience and piety. Hastiness and excessive thinking are not forbidden, but beware of despair and abandoning supplication, as haste might prevent the answer. Strive to research and seek help from trustworthy individuals when choosing a wife, and beware of being overly strict with conditions. Have a good opinion of your mother, repel evil thoughts, and seek refuge in Allah from Satan, the accursed. If it is highly probable that there are unusual impediments, such as magic, then you must perform ruqyah (Islamic exorcism). Be diligent in everything that helps you maintain chastity until Allah facilitates your marriage, such as fasting, occupying your time with beneficial activities, befriending good people, and avoiding lust-provoking stimuli.