First, yes, you are basically B12 deficient. No one should accept B12 levels in the low 300's as normal. Too many doctors are still way behind in looking at the lab ranges without question, despite guidelines from the Family Practice Notebook to numerous medical texts saying that the ranges are outdated. (In Japan, the bottom of the range, depending on lab, starts at 500 or even 550.)

It's certainly possible that B12 deficiency is causing many or most of your symptoms, but so can celiac/gluten sensitivity. Your reports of symptomatic easing after stopping gluten ingestion strongly hints that you need to get a celiac panel done at the very least--B12 deficiency can certainly be secondary to malabsorption caused by celiac (although there are numerous other causes). Other nutrients can be malabsorbed as well, so a good idea would be to get a celiac panel testing transglutaminase IgA and IgG, anti-gliadin IgA and IgG, and total IgA (people who naturally produce low immunoglobulin A levels can have false negative results on the other IgA tests, so measuring that is prudent).

Meantime, continue supplementing with B12--though you're likely to get better absorption with lozenges rather than the spray. The tablets come in 1000mcg to 5000mcg sizes and are quite inexpensive, and are designed to megadose so even if you do have gastrointestinal malabsorption, you will passively absorb 1-2% of the dose and rebuild stores. B12 has no known toxicity level, so you can do 5000mcg/day if you want--some report feeling revved up and energized at those levels, so monitor that.

And, if possible, it's a good idea to get an activated form of B12--methylcobalamin--rather than the cyanocobalamin, so that there are fewer metabolic hoops to jump through in absorbing the cobalamin (which is particularly important if you are one of the minority of people who due to genetic chemistry has trouble methylating organic molecules).