1 inch Logstor is just over 1 inch inside diameter, typical pex here in North America is nominally sized ( outside measurement), flow per gallon rates increase with pipe size as well as fitting sizes, close 90's reduce flow even more, plumbing in series as you appear to have yours is even worse as your plate exchanger then to the hot air exchanger will all have restriction and it all adds up, in a primary secondary loop, the main loop is wood boiler to inside and back to the wood boiler only, each heat loop is simply a set of tees placed closely together in the primary loop with it's own circ to pump from the primary out to the heat load and back to the primary loop, doing this ensures the best possible flow rate from the wood boiler to the home and back to the wood boiler