There is a huge difference between complex carbohydrates bound up in natural fiber and refined starches and sugars. The former are the foundation of the healthiest diets around the planet. The latter are unhealthy. The current anti carb hysteria fails to make a distinction between the two.

I think you'll find you can eat plenty of carbs if you stick to whole grain, unprocessed carbs and also avoid oil. I've been on this diet for two years now and I've lost weight and feel amazing.

You can get enough Omega 3 from non animal sources but if you're worried about it you can supplement with algae-derived Omega 3. Fish get it from algae anyway so you're just cutting out the middle man.

I recommend Michael Greger's book "How Not to Die" for a lot more detail on a healthy plant based diet. I think you'll find it a lot easier to eat this way than you might think.