You would probably need to use a metal chimney liner to do this to meet code. (like when a furnace is vented in a chimney.) But as long as the duct length is suitable for the fan, it might be OK. Check with the specs on the venting table on the fan. Also maybe a quick check with your local codes dept. would be helpful. How/where your other venting appliances vent, and the height of the chimney all are probably factors that need to be reviewed/approved.

BAD BAD idea. It's a fire hazard and a health hazard. It could lead to backdrafting your furnace and carbon monoxide buildup. It also will deposit grease in the flue, and that's enough of a fire hazard in a regular dedicated range vent without hot exhaust gasses from your furnace passing through to add additional hazard to the situation. Plan something else. :)

Decent wall mount hoods are 24" deep - not 18" deep. 18-inch deep hoods are usually the cheap builder-grade hoods or expensive over-the-range MW hoods - neither of which are very effective. The difference b/w an island and a wall mount, though is where the "chimney" is located. On a wall mount, the chimney is on the back of the hood. On an island hood, the chimney is up the middle. I don't see why you can't use an island hood on the perimeter (against the wall). Instead of the chimney going up against the wall, the chimney will have room behind it and go up to the ceiling. I would talk to your contractor about installing it - it may cost more to install, depending on your space and the scope of the other work (e.g,. is the ceiling already open?)

To be even slightly informed about this subject, you would have to read quite a few hood and make-up air (MUA) related threads on this forum. We could also point you to commercial literature that one might extrapolate from. I can provide a somewhat standard spiel touching on the highlights. I cannot provide reviews of hoods I haven't owned. There are two maxims that one might keep in mind. (a) Performance, aesthetics, affordable cost -- pick two. (b) The most efficient hoods (cooking plume capture and containment performance per watt of electricity usage) are commercial hoods. For an idea of commercial hood design and function, read the first dozen pages of the Greenheck Guide, available from: https://www.tagengineering.ca/wp-content/uploads/2015/02/KVSApplDesign_catalog.pdf. What a hood system is expected to accomplish is capture and containment. Capture is effected by having a hood canopy that overlaps the rising and expanding cooking effluent plumes so that these plumes pass into the hood volume, preferably under their own power. Containment is effected by pulling the plumes through the hood filter system -- preferably baffles for most serious hoods -- and thence via the ducting to the outside. Containment requires adequate volumetric flow rate (CFM in the USA). Flow rate achieved depends on the blower selected and the pressure losses moving air through the baffles, through the hood, through the ducting, and through the roof or wall cap to outside, and then, most importantly, the pressure losses in getting fresh outside air back into the kitchen (MUA). Flow rate required depends on the velocity of the cooking plumes and the area of the hood entry aperture. Obviously, one wants the achieved flow rate to equal the required flow rate. But wait, there's more: The specified flow rate for blowers is that achieved at zero pressure loss. The flow rate at some pressure loss is less, just like strangling a water hose decreases water flow. One has to specify a blower strong enough that for the conditions present the desired flow rate can be achieved. (Not otherwise addressed here are the desirable hood features of lighting and blower control.) Fortunately, in many cases we can apply rules of thumb to the selection criteria. Some arithmetic is required. Overlap the hood by at least 3 inches relative to the cooktop or range top on all sides not including a wall. For a 24 inch [front-to-back] range, achieving a 27 inch wall hood may be difficult or interfere with sight lines or head position; in such a case a 21 or 24 inch hood front-to-back depth may do with some plume escape possible. Calculate the area of the hood aperture in square feet and multiply by 90 ft/min to find desired CFM. Multiply that result by 1.5 to roughly find a specified CFM that should work. Choose a duct diameter per the hood installation directions, but the goal is an air velocity in the duct between 1000 and 2000 ft/min. This equals the desired CFM divided by the duct sectional area in sq. ft. Choose duct paths that minimize length and bends, but these are not prohibited. MUA is an entire topic by itself. The goal is to allow air to get from the outside to the kitchen, heated or not depending on circumstances, and lightly filtered, such that the pressure loss from outside to inside is low. In some cases, this may require a blower in the MUA duct. Many simple configurations are possible, along with more complex ones. Search out MUA threads here. Overall, the hood and MUA systems can reach the same price as a high-end range price, and easily exceed the price of an economical induction cooktop.