I am French, and for us weaning is not only about moving away from the bottle to solid, it is transitioning to the big table, so manners are part of it, not only the flavours and texture. We introduce cutlery almost immediately and if you go in any childcare centre at lunch you will see tables and tables of toddlers as young as 14 months eating alone with their forks without the assistance of an adult.
As long as you are giving him nutritious and delicious food, and not falling into the trap of giving him processed snack - even with healthy labels - having half his meal won't affect him phisically.
It's all part of education, and meals is complicated because it plays with out instinct. But in a sense artificially feeding beyond the pangs of hunger goes agains his instinct. Hunger is a feeling that builds up and in active babies once it is placated , they are good to go because that's what most animals do. It is up to you, to create an habit of food at certain times in a determined settings.
Tomorrow, let him be part of the preparation. While you prepare his lunch , say a risotto, or whatever you are doing, have him nearby, pick up the ingredient from the fridge/pantry together, collect the pan, start chopping, and hunger will be stimulated by the noise and smells. When it is ready, serve yourself a small portion and a portion for him.
Give him a small spoon or a dessert fork and help him stab a piece of fish or meat or omelette.
Meals in France take a long time. But as we eat together, babies at the table even if they have already eaten, it doesn't seem long.
When feeding a toddler, when he is done, good, you clean up and kitchen cupboards stay close until the next meal.
You are correcting an habit and teaching him a skill. It is fine to give him something in his hands to explore, such as a whisk from the utensils drawer, while eating, but that's different than creating a story and show and reading 8 books.
Children have their own personality and ideas. Sometimes - very often - their wishes clash with ours or what is expected of them. You teach from a young age, what and how can be done their way and what and how cannot. Can be the food without entertainment , the seat belt, the junk food at their eyes level at the supermarket .....
Someday, after lockdown madness, you will want to meet up with friends in a cafe or picnic, and talk to them instead of producing a show.
You had success today : 2 out of 3 meals went well. When to comes to babies and children, magic doesn't happen overnight.