Hello Frank, don't worry the situation is fixable one way or the other.
I need a lot more data from you however.
1. 4 photo's of the boiler and pump room taken from oposite angles so that I can get an idea of what you have.
2. A sketch of the hydronic heat piping layout in the house, and size of the house, and nearest city so that I can assess the load conditions.
3. I need to know if the tank is an open top tank or closed top, I need to determine if it is a closed loop system or an open loop system.
4. I need some photo's of the radiators.
We can start there, so far I suspect air trapped at one or more high points in the system, and possibly the piping undersized adding pressure drop, compounded by the extra heat exchanger doubling that pressure drop... its all mostly fixable however.
We can go from there... for your offered amount I will do the analysis and make some recommendations, if you want systems engineering with several CAD drawings, I will submit an additional services offer for that.