I'm veggie over 30 years. Unnecessary fussiness (we all have certain items we really can't bear and never will like but I suspect there's an element of his being allowed to get away with eating something fine one week and not the next?) is not going to work. To do vegetarianism properly and healthily you have to eat a wide variety of foods and ensure you're eating foods rich in nutrients that you previously would have got from meat.
I would sit and have a serious conversation with him about:
The health and nutrition aspects
That he needs to stop the fussiness
That he needs to cook at least one meal a week for the family himself (compromise goes BOTH ways)
That he needs to appreciate your efforts, it's not easy juggling veggie and omni diets in a household PLUS the mental load aspects
When I went veggie my mum said "fine, but no way am I cooking for you every night. If I'm doing something you can eat then you eat with us but otherwise you need to sort yourself out" which is absolutely fair enough.
She gave me a budget for my veggie things (and this was WAY before Linda McCartney let alone quorn! This was in the days of unflavoured, unseasoned dried soya from a health food shop!) and I was free to use whatever other veggie items were in the house - vegetables, eggs & dairy, stuffing etc
I was batch cooking and learning how to use the soya and things like beanfeast and sosmix
Another condition was she had me go to the drs and get my iron and vitamin levels checked and dr chatted with me about the things I needed to be careful of (making sure I got enough iron and b vitamins mainly) and I was to go back and have my bloods checked again after that first 6 months - this proved interesting as I'd had issues with anaemia previously and what happened was my iron levels IMPROVED. But I have a theory on that which is a personal quirk.
She even had me get books from the library on going vegetarian and how to do so healthily
All of that has stood me in good stead.
In terms of meal ideas well a good mix of:
Pasta - with tomato, roux or pesto sauces but with plenty of veg too, spinach works wonderfully with many pasta dishes
Stir fries - home made sauces are easy enough but there's loads of good ready made ones too, a good variety of veg, throw in some less commonly used ones that he likes, I've treated myself to some bamboo shoots and water chestnuts recently, tons of veg works in stir fries
Soups/Stews/casseroles/curries - great for more wintry/root veggies, pretty much anything goes and soups especially are great for "disguising" less popular but healthy ingredients. My non veggie but kinda fussy dd has been eating spinach, kale, peas, celery, spring onions, beetroot, mushrooms for YEARS without realising via my "magic" soup which she always eats 2nds and sometimes 3rds of but if you asked her if she ate any of those veggies she'd say no 
Cous cous dishes - super quick and easy and will work with pretty much any flavouring/sauce and many different veggies
Egg dishes - tons you can do with eggs and they're also rich in iron and b vits. There are the standard scrambled/fried/poached varieties but there's also things like huevos rancheros, and my own favourite - baked eggs! Super easy and delicious
Pies/tarts/pastries - homity pie, quiche, veggie tart, cheese tart,
Samosas, spring rolls, spanakopita, I've even some veggie gyoza in the freezer at the moment!
Snacks and lunches - sandwiches don't have to be boring cheese or egg, there are veggie spreads and pâtés, sandwich spread, marmite then there's crackers or wraps done in a million different ways, grilled/roasted veggies work in sandwiches and wraps, or "on toast" beans, eggs, Tinned pasta, Tinned tomatoes, or jacket potatoes with numerous toppings...
Hope that gives you some ideas
I managed for many years cooking for omni dd and I, sometimes I'd do a meat option for her and veggie alternative for me (eg meat sausages for her, veggie sausages for me, mash and beans) or she'd have a veggie dish with me (chilli or pasta and sauce) or I'd use up leftovers from batch cooking so a veggie casserole for me and a meat one for dd so it can be done with collaboration and planning