You're describing my situation exactly as far as the relationship between my cat and yorkie puppy went a couple of months ago. My cat joined the family when she was about 10 weeks old and was introduced to my adult shihtzu almost immediately. That took all of a day for them to get used to each other. Of course, my late shihtzu was eager to make new friends and never barked at her, and there wasn't any amount of hissing or growling on the kitten's part. We let the kitten approach the shihtzu and not the other way around throughout the first night confined in my bedroom so that we may supervise their interaction at all times and they'd also be forced to be in each other's presence to give it a chance.
Forward to 8 years later. Shihtzu is no longer with us. We bring in the 4.5 month old yorkie. Packed them both up the next morning and took them both to "neutral territory" which was my parent's place to introduce them. Okay, my cat's been there before so she still remembers the family and the house, but she doesn't see it as "her" place at least. Not sure if that made a difference because for the next few days, she was miserable and I was nearing tears thinking it won't ever work out. My cat was acting exactly like your ragdoll boy. She NEVER hissed at mommy (or anything except my brother's cat for that matter) and NEVER heard her growl before. She'd go into hiding to the point that for two mornings, we thought she had jumped out the 2nd story window and ran away! She's been a 100% indoor cat. Of course, we found her 1st hideout eventually... then her 2nd, etc. I still remember the night I took her to a different room separate from where the puppy was at. Carried her in my lap which she normally LOVES but all she did was keep growling non-stop the entire 10 minutes I sat there soothing her and loving on her. That really broke my heart. At the same time, I couldn't help but think how CUTE she sounded as I've seriously never had her do anything other than make little squeeks resembling "riaow" to get her point across. She still refused to come to bed with us (where the puppy's been sleeping as well) when that's all she ever wanted to do since we've trained her NOT to lay in mommy & daddy's bed 1.5 yrs ago.
Day 4 - Progress! They finally met nose to nose! Once she let that happen, the puppy stopped barking at her and was super happy just to sniff (later evolved into excessive kisses on the face until she has to get bopped on her head by the cat to just stop already
).
Day 6 - Our cat finally joins us on the bed! Sure, it's the opposite side from where the puppy slept but progress! Puppy doesn't try to pounce her since the cat's been tolerating their close proximities whenever they're both hanging within a few feet from mommy & daddy.
Day 7 - Cat takes interest in puppy feeding time and tries to get some of the good stuff too... already started drinking out of the puppy's water bowl.
Day 8 - Cat starts taking interest in the hard pet carrier and even went so far as to sleep in there while puppy just sniffs around all nervous and shy-like, wanting to play while cat's ignoring her. The cat starts a "hide-and-go-seek" game with the yorkie, but alas, that doesn't seem to be her forte... I question my precious yorkie's eyesight and attention span LOL.
Fast forward a couple of months - Yorkie's now a little over 7 months old. They now play chase whenever the cat feels like it, and that doesn't last long usually and ends with my cat sitting there with one arm curved around the back of Pichu's neck to hold her down since she won't stop hopping up to lick the cat's face. When that doesn't work, she takes a gentle nip (no puncture, no marks whatsoever) of Pichu's ear. Pichu yelps and stops long enough for the cat to dash away while Pichu wants to resume the play.
So anyway, I remember reading on here how it took the person about 4 days for the cat to be okay with the new family member too. So I think that might be the magic number when you might start seeing changes! 4-7 days for peace of mind and a happily ever after household.
I feel for you! Good luck!
Edited to add: What will happen is, your cat will learn to either ignore the new family member, tolerate her, or love her. Either way, he shouldn't be staying miserable forever~! They learn to live on higher ground where the pup can't reach.