Simba will be okay. Just don't go overboard like I did. My dog Scooby had a stroke and was no longer able to go out the doggy door or upstairs. So what do I do??? I buy a bigger house with a big back yard for him and Shaggy! (Dirtnap came later) How spoiled!
Well, short of lowering your furniture or purchasing a new home. Maybe learn to compensate for Simba's limitations. I pick Scooby up if he can't get on the bed after a few tries. I make him try first! Check Simba's paws. Maybe they are cracked or have a splinter? Feed Simba some supplements. Maybe it is time to change dog foods to senior dog formula. How is Simba's weight? Scooby is a little "Fat Boy" and that causes some of his problems.
God Bless Simba and you!!! Take care of you both!!!