I'm sorry about your health issues.  It is a shame that healthy food is more expensive than fast food, isn't it?  But in the long run eating healthy food will do a lot to cut down on healthcare costs.

That is great that you have a farmers market nearby!  Vegetables and fruits are always cheaper that way, though organic ones can run higher.  the healthiest vegetables, ie greens, tend to be the cheapest so that is good right?  Collard greens, bok choy, kale, and broccoli are all excellent sources of calcium and numerous other nutrients.  Green beans, celery, carrots, potatoes, sweet potatoes, mushrooms, green bell peppers, lettuces, and other vegetables tend to be cheap.  Fruits can be more expensive but bananas are reasonable.  I like to buy a whole cantalope or pineapple and then chop it up and eat it for snacks or in stir fries throughout the week as opposed to buying canned or precut ones which can be more expensive and don't last as long.  It keeps in the refrigerator in a tight fitting container for a week after being chopped.

Pumpkin seeds and sunflower seeds are reasonable as far as cost.  Flax seeds (a coffee grinder can grind them for you) are relatively cheap bought in bulk also and can be added to oatmeal or other dishes for a boost of omega 3s.  Oats are cheap, as is couscous, especially if bought in bulk.  Dried beans are very cheap.  One 1/2 cup serving of beans (kidney, chickpea, white, black, pinto etc) is about 6-8 grams of protein, comparable to an egg or hot dog, but without the cholesterol and fat, and with fiber and other nutrients.  Lentils are about 8-10 grams of protein per 1/2 cup cooked serving.  Beans can be incorporated into soups, dips and spreads, vegetarian sandwiches, stir fries, baked goods (as an egg replacer) or eaten as is with salsa, catsup, molasses, or other foods with them.  Nutritional yeast is a food that is often used as a "cheese" for vegans and if you can find it it is reasonable in cost.  The trick is finding it.  Most natural food stores sell it.  It is fortified with B12 and has 8 grams of protein for a few tablespoons and adds a nutty flavor to foods.  Mixed with ground up almonds or cashews or walnuts, it can be used as a "parmesan cheese" for texture.  And of course, brown rice is very affordable.  Even frozen vegetables are relatively cheap.  You can make a meal by mixing some beans, steamed or boiled frozen vegetables, and cooked rice and add some tomato sauce (canned tomato sauces and pastes are very cheap too) and nutritional yeast, maybe some fresh basil leaves or oregano seasoning.  Even throw in some fresh pineapple for an unexpected twist.  I can picture this dish being good with black beans.  Another one is split pea soup.  Split peas are very cheap and high protein.  I simply saute some onion, garlic, and carrots in a nonstick large pan with a little water or oil, and add split peas and then water (about four cups) and let it all simmer for a half hour.  I add lemon juice and other spices, then blend the soup in a blender (a regular cheap blender will work) for a creamy rich soup that is VERY filling.  It makes four cups and probably costs less than $2 and provides tons of nutrition.  

I really like the Vegetarian Resource Group and Journal because they focus on very simple healhful foods for vegetarians and vegans that are economical.  Might be worth looking at.  no need to spend a fortune on designer fake meats and cheeses which tend to be high in sodium and devoid of nutrition.  The best foods are the simplest.  Even a plain potato can be baked and then add steamed broccoli, nutritional yeast sauce or a homemade gravy/sauce, maybe some beans, and you have a filling meal.  You can make a homemade sauce with just roasted red peppers and cooked softened cauliflower.  Once the two are softened by cooking, blend them in your blender with spices such as garlic or onion powder.  Another one is cooked carrots blended with dried coconut and a plant milk such as soy or almond milk.  Makes a nice sauce to go over beans and rice and a leafy green or other vegetables.  Blend a few tomatoes with an orange or other fruit and use as a dressing for a garden salad.  Adding seeds, beans, and fresh fruit to vegetable garden salads makes them very filling and tasty without needing to add designer commercial dressings and other junk.  

Hope this helps!