Personally I would not do what you are trying. For a whole bunch of reasons. There is nothing wrong with the basic concept - wood heat for radiant system. The devil is in the details.
You really should have intermediate storage. A loop for the wood burner with antifreeze in it, a large insulated storage container, and a circulating pump between the boiler and storage. This can be unpressurized. And that will help avoid explosions if you are also not clear on relief valves or they get frozen.
Then a heat exchanger in the storage tank piped into your existing system and a circulating pump driving that loop.
Then all of the controls and electronics necessary to merge the functions. And something to avoid boiling water in your wood boiler.
Assuming things freeze, you should not be using plain water in the boiler unless you drain it when it is not in use or make sure it is always keeping all the exposed water containing equipment warm.
You migh consider bringing in someone with experience with this sort of thing to at least provide you with a diagram that will work. I am surprised the boiler vendor does not provide more information.