Hi Greta, I really sympathise as I have just switched to ff from bf as I'm going back to work, and reverse cycling was just ridiculous with dd taking minimal formula during the day; pumping not practical. I too am v sad at stopping and had lots of similar questions esp re feeding to sleep.
To answer some of your questions, it was a struggle to get dd to accept a bottle but she got there eventually. I mixed ebm with formula (prepared!) and over time increased the proportion of formula and it did the trick. She didn't have the ability to suck a teat initially but nuk teats and putting pressure on her cheeks (trick used to get preemies to suck) worked.
She (still) will only take formula quite hot, so I make feeds as I go; at home with water from the kettle and cool under a running cold tap; out and about I bring a small thermos of hot water, sterilised bottles, and a little formula dispenser that you measure scoops into in advance. Really quick and easy!
I found that dd definitely doesn't get comfort / fall asleep on the bottle. She would always feed to sleep before so I now rock her to sleep (it has only been 5 days since I stopped feeding at night). I won't lie, the first night was brutal - many hours of crying and rocking. She is 21 weeks though so I'm sure you'll have an easier time at 13 weeks. When she has had enough she turns her head away and purses her lips; it's pretty clear. She doesn't comfort suck on a bottle, and doesn't take a soother. She gets great comfort from a couple of bunnies that I've used for ages in cot, pram etc, but doesn't comfort suck them or her fingers yet (hoping she'll start). You could cuddle one when you bf (I also sprayed milk on mine!) before stopping, I think it would help?
I hope some of this is helpful! It is some of the info I wish someone had given to me when I was working up to stopping. Good luck, and keep remembering that you are doing it for the best if that's what has been advised. 