Your model looks really good.
You are using blender I see.
First up, I find it is easiest if you size your model based upon the squares in blender being the same as the squares in the game.
Once you have the size you want you need to then centre your main object model at 0,0,0, then select the objects and click Object - Faces - Apply - Location and Apply Rotation & Scale.
Add points to your model:
In Object mode, 'Shift+A' to Add - Empty - Plain Axes. Rename this to 'points', centre this also at 0,0,0. Add in more 'points' and put them in places around the building depending on the use: name them 'build_001', 'build_002' etc, these are the points at which the builders work from. 'use_001, etc, is used for marking positions of work carried out at building or for entry to house (I think . maybe someone else can confirm this), plus there is smoke_001 which is the point where the smoke exits building if you have a chimney. Once all the points are made, group them all under the 'points' plain axes.
Save you file.
now the way I do it is:
I delete all the 'points'. Export the file as an .fbx, don't save.
Reload up your model, now delete all the objects and only keep the 'points'.
Now export the points only into a .fbx file.
Start a new empty blender file, import .fbx, bottom left of screen, change the Scale to 0.01 - import each of the .fbx files you created earlier at this scale, everything should already be in the correct spot, zoom in to see your now tiny model.
Select objects and add materials if still needed (make sure you name your texture image files the same as the material and texture holders in blender. (see this post Banished modding and Blender
Now export this as an .fbx. leave scale at 1.0 this time. this should be your final model.
Now make sure you have all of your code correct.
You will need to make material files for every image that is called up by your model.
So if you see within the building/apiary example (ignore the honey files), Models/MaterialInstance folder there is images and .rsc files, the apiary only uses one texture image for the whole building, if you have done the same it should be pretty easy for you to alter all the files, edit all the names within the MaterialInstance .rsc files to link to your own textures. If you have multiple materials/textures for the model, you will need to make .rsc files for each of them within the MaterialInstance folder.
One folder back (Models), is where your exported .fbx file goes, you will also need to have all of these .rsc files edited to link to your own files.
Copy the wood/stone house template .rsc and use this as the guide for making your own. Change all the parts needed to point to your own model (the house templates are calling up different models for 'F-key' variants, that is why there are multiple meshes etc listed just delete them extra ones so it is only calling up your own model.
You also need to make your own SpriteSheet + toolbar icon (goes into UI/Sprites) and StringTable files within the UI folder.
Also needed is your houses toolbar file. Like the example/building/apiary.rsc file, this is where your model is called upon and adds the icon to the game toolbar.
If you have certain issues let us know, happy to help.