Your snoring likely has several contributing factors working together: chronic nasal congestion from allergic rhinitis (consistent with your dust and pollen allergy), mouth breathing, and recent weight gain, which is a major risk factor for narrowing of the airway during sleep. The choking episodes, gasping, dry mouth, morning tiredness and "foaming" you describe are concerning for obstructive sleep apnea (OSA), which needs proper evaluation rather than self-management.
Next Steps
Please see an ENT in person for a nasal airway examination, and get a sleep study (polysomnography) to assess for OSA given the nighttime choking and daytime tiredness. Alongside this, allergy management for the rhinitis and a structured, medically supervised weight-management plan will help address the underlying causes.
Health Tips
Please do not ignore the nighttime choking and breathing difficulty - the sleep evaluation should not be delayed. Treating allergies (e.g. nasal steroid sprays/antihistamines as prescribed) and gradual weight reduction often improve symptoms significantly.