Is that 7500 square feet of space with 8 foot ceilings or does the house have two stories or one main floor and living in the basement, add all the footage, with two shops and a house 7500 isn't much, if the shops have 14 foot sidewalls you should figure two levels or a building thats 50x50 with 14-16 foot sidewalls is 5000 square feet alone. I've run my OWB for about six years now and love it, it paid for itself in less than two years, I went with a wood doctor with boiler plate steel in it and a 20 year warrenty, we heat the water and run it year round. First off find the one with the biggest door made, don't get hung up on the lenth of wood it takes but more so the height you can stack it. with that said, wood doctor makes one with a double door in the front, the one I should have bought and I could load large chuncks with a skid steer and pallet fork instead of by hand, the length does very little for you, its nice in theory but unless its cut split and shoved in very neatly your not going to get it full anyhow, Mine has forced air and you want that with any of them you look at, the greener the wood the better for mine, you burn less green cut wood than dry wood, there's more btu's of heat in green wood than dry, unless you have a forced air system you can't burn green wood very well, with that said mine also burns more wood than others the same size.
I looked at central boiler, they make a good furnace but their contols are electonic and some have a computer in them that I looked at as well, the other problem is their forced air tubes are at the bottom of the furnace and you have to have most of the ash out of the furnace to get them to work unless they changed this design, mine is in the door and your having to pull the coals forward before you load it every time is all, if its natural draft leave it at the dealers lot in my opinion but thats me. I"m also not big on pressurized boilers but they are better for lasting that open air one's, they supposedly won't rust as fast but also cost more and more dangerous to operate so unless you know exactly what your doing I"d opt to avoid those.
I use a heat exchanger in the house and also a sidearm on my waterheater to heat the water, I don't yet have my shop done with infloor heat but my office is done and I love my infloor heat in that, we just haven't had time to finish the shop part yet and when done I"m going to heat almost 9000 square feet plus another house and that would be about 3000 feet more but we're wanting to see just how much it takes to heat my shop first before hooking up another building as well. I'm not sure what sizes your looking at but go bigger than you need or anyone recommends otherwise your loading it constantly, like 3 or 4 times a day, we load our twice morning and night and thats enough in my opinion.
As for heating with wood so much cheaper than gas, yes, but its still not free, I"ve got almost 20k tied up in everything we use to heat with, and then we won't even start on how much it costs and time involved to cut, split and haul the wood, we used to live in a rented hotel of a house that one's before us said took 4000 gallons of lp gas a winter to heat so you didn't freeze to death, not warm just enough so it didn't freeze, we burned almost 35 cords of wood a winter to heat it to 75 degrees day and night, but spent almost all winter cutting wood to do it, now we're in a house thats way more efficient to heat and are down considerably, once my shops done we'll probably be back up to about 20-30 cords a winter again, so unless you have plenty of time and enough help most get sick of it pretty quickly. I'm gonig to get some kind of firewood processor to speed things up once we have some money saved up, right now we've got kid help but they are graduating and leaving home shortly and we're back to working it all by ourselves again, my wife and I that is. Make sure you have access to wood free and for the next 20 years and have it accessable year round with no problems of getting there to get wood. Don't ever put in any kind of indoor furnace, we heated with wood in the house all the years of growing up and in one rented house we lived in for a winter, never again in any house outside is the way to go.
Best of luck on whatever you find and get.