Hi mate feel your pain, my partner was diagnosed with alzheimer's in 2012 and i cared for her almost single handed for 6 years, loved her to bits and felt no one could look after her and love her like i did.
by autumn 2017 it was apparent i couldn't cope anymore and we (myself and her adult children) made the agonising decision to look for a care home for her.
She went into care in Jan 2018 (a day i still think about all to often)
She was well looks after but in the summer stopped being able to eat and drink and passed away in July 2018.
Miss her every day but have great memories and did the very best i could for her,
Don't feel guilty you obviously have reached the point where you can't hang on any longer,
i was in the same position and held out to long really for the reasons stated above
If you know in your heart you did the best you could/can you have to let go and let the experts take up her care,
Again all the best