Have you been able to get specific on what your triggers are in terms of fat? Eg, when I was struggling with gall bladder issues, yes, I needed relatively low fat, but fat in cows cheese was particularly bad, as was red meat. I could eat white fish but things like salmon tended to make me feel ill. But chicken, even the "fattier" bits like thighs weren't a problem.
I also didn't have a particular issue with fat in the form of olive oil so, for example, ate quite a lot of roasted veg on pasta with just a bit of sheep milk feta cheese and some avocado.
Its also your choice of carb that can make a difference. I ate a lot of rice in those days as my body could process it better vs potatoes or pasta. Bread, weirdly, was okay, but in relatively small amounts.
Re ideas,
Roasted veg (you can use very little oil to keep it relatively low fat - if you up the number of tomotoes, it stops it from getting dried out). [edited to add: if you make large amounts of roasted veg (be generous with garlic) you can use a blender and a bit of low fat cream cheese to create a sort of thick paste which goes well as a side dish with meat and fish. Again, the trick is to ensure a high ration of tomoatoes for sweetness and liquid. A bit of balsamic vinegar in cookin ghelps too]
Low fat cream cheese has a slightly tart flavour which actually lends itself to certain things. I often use it in pasta sauces to add a bit of cheesy creaminess without extra richness - to a tomato based sauce in particular.
Grilled fish is great, and filling,but increase portion size. Often fish comes in tiny portions which are not enough to be filling or to generate enough calories. Serve with n ew potatoes and veggies.
A great basic low fat salad dressing I do often is lemon juice and fat free greek yoghurt, sweetened with a bit of honey. Add some mustard, some dried herbs, salt to taste. Works on steamed greens as well.
On that note, greens are often a lot more flavoursome with fat but to reduce this, rub a little oil on them then cook them in a hot pan to get a bit of colour on them. Then add a bit of water and put a lid on them to finish them cooking. You can then flavour them at the end with: a bit of garlic, lemon and honey (let it caramelise in the pan quickly with the veg at the end) or fat free greek yoghurt with a bit of tahini mixed in and some lemon juice or stir some miso through it.