Good things take time ;) Add castings if ya got some :D

What is a "garden box"?

What do you mean when you say you "lose soil"? Where is it going?

Sounds like you are treating your garden box as a composter. That's fine. However, as far as I understand it, that will generate mold and all things associated with things rotting. I have tried tomatoes many times and have now given up due to mold and similar problems. If you got a tomato variety that's immune to that, that's great. Re. the unfinished stuff come next March, I would just rake that away as far as possible or or even move to the opposite corner of the garden. I think you should stop adding NOW so everything will be done by next spring. Get an old garbage can or any container to serve as a worm bin and put your scraps there. By the end of next tomato season, you could dump the finished stuff to your garden box, and rinse and repeat.

Nothing wrong with composting or feeding worms right in the garden. Tho you may not want to put things with seeds like tomatoes in as they will not compost and likely will germinate in force in time. I like to spread those volunteer seeds around.

<is there anything I can add or do that will speed the composting up?> My standard answer to that question is - If you need compost in two weeks buy it. Nature takes time so planning is key.

throw blended scrapes into the bin that worms will find it easier to work with

Horse apples. Worms' favourite. Also good for your garden.