When to put dog with CHF to sleep?

My senior dog (15 y/o chihuahua) was diagnosed with left-sided congestive heart failure back in 2023. Since then, he has developed a severe heart murmur, pulmonary edema, and a bad cough. He’s been on vetmedin and furosemide for a while now, and his doses have been slowing increasing since then. Within the last few weeks/months, hes been struggling to get on/off furniture, rest without needing to get up to cough, and exercise normally. Last week while a few minutes into a walk, he suddenly collapsed/fainted and urinated over himself and needed to be carried back home. His breathing is regularly labored and his coughing episodes are very intense and are painful to hear. I’m wondering if it may be best to put him to sleep sooner rather than later, and would greatly appreciate any advice on the topic. Thank you 🙏