Paris Coffee Shop

How much meal and spending money should I take to Paris, France?

I am planning a 3-day trip to Paris, France; 5-day if you include the flights to and from Paris. I am going solo by myself; the tickets for my flight are going to be $799 roundtrip from Phoenix, AZ, USA and I am planning to leave the last week of April next month. I’ve found a hotel for my 3 night stay in the Montparnasse area; it’s going to be about 339USD (a hotel is just a place to leave my bags and sleep) and is located near a bus and metro station which I will be utilizing as much as possible as I also am getting passes for transportation to and from the airport and just to generally get around town. If all goes as planned this will be my very first time going abroad to Europe, out of the States, and into France (been brushing up on my Francais also). I am going to France to mostly experience the culture rather than shop till I drop and splurge. While I’m there I want to take pictures of the architecture and city, use my L’opentour vouchers to ride the bus around the city and cruise the Seine, visit significant sites(and try not to enter museums; I will visit again this is just a mini trip for now), people watch, eat, communicate with locals, and just overall BE by myself and dip my “toes in a lake of culture”. I seem to have everything planned out but the only thing I am worried about is expenses such as meals, groceries, and souvenirs. I want to try French food but not go overboard and spend $30+(excluding the tip) on one meal sitting; for breakfast I’m think bakery or market fruit, for lunch I’m thinking restaurant for lunch specials, and for dinner I’m thinking something generic like fast food(haha??) or deli.
I would like to know the average costs of: (if possible, answer if you can)
Pizza (by slice or whole)
Croque-monsieur
Crepes
Salad(w/chicken)
Croissants
Pastries
Muffins
Coffee
Fruit tarts
Crème brulee
Bottled water
Yogurt
Any type of breakfast sandwich like a mcmuffin (I’m a breakfast person)

And as for souvenirs I would like to buy post cards, t-shirts, or even get my portrait drawn by a Parisian artist. I am also dying to go atop of the Eiffel Tower(is there an admission price??). How much do you think I’d need to bring for meals and spending money? Your answers are greatly appreciated:) Sorry if I seem very Americanized (because of my fastfood cravings); my mind is open so if you can refer me to good places(restaurant, café, or deli-wise), that fit within my budget range, please do:D