If you have the possibilities to fix it up I honestly recommend you to do it. As you described before you could start with the engine (0 incidence) I am not really sure where is your primarily basis of your measurements, but I would not take the main wings because they always have incidence. Forget about the wash out by now. Luckily your stab could be at 0o incidence (It is in a great number of ARFs) and often it is built into the primary line of the plane which is 0o incidence. If so, then position your engine to 0o incidence and check it out, see how it flies, if that simple fix repaired the issue congratulations, if not, the you will have to shim the wing saddle of the main wings to achieve a desired incidence.
I had a Phoenix low wing Sonic and it had an incidence problem. A buddy of mine also bought another Phoenix model and had to do some changes to correct the incidence. Be aware that in the world of the ARFs, this kind of problems are very common, many people just use the trim and they fly acceptable, but if you really want to fix your plane and want to have the best of it go for it, you will learn more than a simple fix.