I had a fold up high chair when my grandchildren were very little as it did confine them when eating. One thing I am quite strict about is that as soon as possible food is eaten sitting at the table, not wandering around or sitting on the sofa etc. If you don't want to purchase or borrow a high chair sitting him on the floor on a plastic tablecloth is probably easiest in the short term.
A plastic plate with an assortment of finger food is the best option for a child who doesn't like to be spoon fed but he must stay seated. If he moves off the plastic take the plate away. Veggies like carrots, capsicum, cucumber etc cut into strips, cut up fruit like peeled apples and banana pieces, dried apricots, sultanas, small pieces of omelette, cheese, sausages or chicken in bite size pieces, small sandwiches, toast strips provide a healthy varied menu. Water in a lidded sipper cup can be placed nearby.
Don't make a fuss about using spoons or forks as this makes meals a battlefield which is the last thing anyone wants. Some children just like feeding themselves, often very independent kids, when he's ready he'll start using spoons and and forks like "big people".