I don't think abom lona is broken. Deepone Lona's summons lets you take out everything without ever putting yourself at risk and most fights end with just the 2 meaning you only spend 20 stamina and Deepone Lona is trivial to unlock thanks to the shortened pregnancy duration. The cost of Deepone Lona is needing to use a blue pot everytime you want to interact with NPCs.
Compared to that, Sickly everyday is a huge, huge pain in the ass because you lose stamina every second just for standing still and Abom Lona has to get into the fray and get damaged and all that unlike Deepone Lona. I can take out that giant in the Arena as Deepone Lona with only 40 stamina at level 15 while I couldn't with abom lona.
So Abom Lona is fun but nowhere near "broken".
Anyways.... have you tried getting Lona parasited? Free corpses to desicate everyday so it might completely remove the day 2 day cost of abom lona especially since you'll probably make up all the lost health from sleeping with 0 food. It also fits her theme cause them parasites are abominations.
That... doesn't make a whole lot of sense. First of all, Sea Witch skills are Wisdom-dependent. Second of all, the summoning spell is basically the only thing you'd ever transform for anyways. Sure, it allows you the ability to clear most dungeons safely, but your summons attack everything that's not you indiscriminately, including escorts, allies, and people you might want to rescue. And the argument that Deep One Lona is more stamina efficient and doesn't need to take hits makes no sense to me. As an abomination, you can play any build you want and still eat corpses. It's just nice that it's melee-friendly too, and even then, eating corpses more than makes up for the potential health and stamina loss. Sick is only a pain in the ass if you actually are just standing around. It's a nonissue if you're running into things to kill.
I also don't understand why you're using The Beast as a measuring stick because 1) The Beast isn't your typical enemy, and 2) you can just kill him with whatever you want and eat him after if you're quick enough. With his high ass stats, there shouldn't be a net stamina loss.