Mayness, I would definitely recommend going vegetarian out of those options -- I did quite recently (it's been 3 months now) and it has been a huge catalyst for me to lose weight. I know exactly what you're talking about when you say you want to avoid boredom and you think restriction will help -- it really does! But IMHO it's healthier to restrict a category of foods that can be effectively replaced, nutritionally-speaking. You can get vegetarian protein without really shocking your body all that much -- carbs are a source of food for living (and important for exercise).
Also, I've found that the ethical justification for vegetarianism is a *great* way to stay motivated -- you can think about it as more than just doing it for you, which helps you stay on plan *every meal and every day*.
This is more radical, but you might even try to be as close to vegan as you can for a couple weeks just to see what new foods and habits it forces you to try -- I'm not vegan right now, but when I tried it I discovered a lot of great foods that helped my weight loss and that I still love:
--
Salads without ranch, honey mustard or other cream dressing!! I now use a combination of heirloom tomatoes, beets, onions, and various vinaigrettes for flavoring.
--
Fresh fruit and granola instead of cake for dessert.
--
Organic peanut butter and fruit preserves instead of cream cheese on my bagels -- for me, it was much more filling. But obviously peanut butter is still fatty, so in small quantities...
Mainstream American diets are so reliant on making meat, bread, and butter the centerpieces of the meal that it becomes hard to "untrain" yourself from them. It looks like the foods that made you go off-plan were mostly carbs of the kind that include dairy, so maybe cutting out dairy entirely for a few days would help you figure out substitutes you can keep in general!

(Of course, do NOT do what my vegan friend did and buy vegan desserts -- that would be counterproductive, because then you'll feel pressured to eat them...

)