Now that we know your size, it's clear that kayak is way too wide and deep for you. Shame on the salesperson that let you buy it! I hate to say it, but I doubt all the lessons and paddle exchanges in the world will help adapt that boat to you. You might try adding some padding to the seat and sides to fit yourself higher and more snugly centered in the cockpit. You might even have to switch to a canoe paddle -- honestly the dimensions on that craft are more canoe like than kayak like but with the downside of you being seated too deeply inside and having the cockpit coaming restrict your reach.
My suggestion, instead of continuing to struggle with it, would be to see if you can return it and get a boat more suitable for a petite person or, if they refuse to exchange it, sell it on Craigslist and find a lower volume boat.
See if you can get LL Bean to refund your money and then go to Collinsville Canoe and Kayak (in your state, just west of Hartford near Canton). They are selling off their boats at end of season and have a new Dagger Approach, which could be perfect for you. It's marked down to $559 from $699, is 9 feet long, has a skeg for tracking and is designed for smaller adults with a 25" beam. Only weighs 38 lbs and has bulkheads so you won't have to buy flotation bags. It is much better outfitted than the one you bought, including having thigh hooks to help you control the boat (missing feature in the Manatee). Look at the details on the Dagger link I sent you. Collinsville C and K's shop is on the water (lake?) so you can test the boat right there.
Call first to see if they still have it. That's a good price and a nice little boat. You could even use it in mild whitewater (lots of nice rivers of that kind in your area) but it is said to perform well in flatwater too. If you decide you want to go to a longer boat later on this one will have a higher resale value than the Manatee.
Maybe a grip change will help I used to paddle with my thumbs wrapped around the paddle shaft. I found that gripping the paddle with my thumbs on top beside my fingers relieved the hard grip on the paddle and stopped the “tennis elbow” symptoms as well.
Agree with willow leaf Do what you must to get into a boat that fits properly and get a short, light paddle. You’ll never be happy with what you got from LLB.