The HydraStar Disc Brake Kit w/ Actuator for Tandem Axle Trailers # HSE7K-T1 is designed to work with a standard style breakaway kit like you have currently so it would work well with what you have. For more info on this kit check out the review video I attached as well. view full answer...
Could it potentially be used as a replacement, yes. Is it a "direct replacement"? No. I was not able to find a ton of information on the Atwood OD5001 water heater. But from what I could find, it has been discontinued for a minute and you will likely have a hard time finding a "direct replacement".
From what I found on your OD5001, it measured 12" tall x 12-1/2" wide x 14-1/2" deep. The Furrion RV Tankless Water Heater # FR68SR you were looking at measures 12-5/8" wide x 12-5/8" tall x... view full answer...
Thanks for the picture of your Lippert Equa-Flex equalizers and listing the capacity of your axles at 7k. Based on that we know that the kit you need is the part # LC279688. view full answer...