"it is a parents job to provide healthy nutritious food (not meals
) for children, it is the child's job to decide when & how much they eat" - If you offer less healthy food they will want it, but if you stop it they can want it even more, it is finding the balance that is important.
I recently met a lady who has a 6yo a 8yo & a 10yo... before they started school they only sat at the table (as a family) 2x week, everyone sat down & they ate favourite foods (mother would even cook 3-4 different foods to ensure they all ate... now they sit down & eat pretty much every day. Her logic was they learn the habit slowly & build on it & it really seems to have worked.
Around here my 2 children (almost 3 & almost 5) can have 2 "sugar foods per day" they can't have it at breakfast, but they can any other time of the day, those sugar foods include anything from icecream to chocolate milkshakes to jam on sandwiches, cake & cookies to "junk food" & soft drinks & generally they choose to have one earlier in the day & depending on what they know is on offer will wait for Daddy to be home (ie after dinner) or have it at afternoon tea time. If my children don't want the meal I have on offer they can have a cheese sandwich (so can dh for that matter... that has only happened 2 in our time together LOL) but they can't skip the "savoury" at a "meal" for the sugar food... they can just have a sugar food for a snack though.
I do think strapping in a chair causes a power struggle & potentially could result in eating issues. I do think you & your dh need to work out where you can find a meeting point & stick to that. Eg I've heard of people having "cake day" & so the children know on those days they can have cake even if they don't eat dinner & other days - no cake no matter what.