If you add a little HCL in the micro mix, then you do not get that funk in the line........
Also, more dilute solutions make it easier to use timers and dose more volume and more precision on the amounts that you dose.
It's easier for most any system to dose a larger volume more precisely.
3.5 gallons per hour is pretty low, so a simple timer with 1-15 min increments (intermatic digital etc) can be programmed to dose 220 mls at zero head.
Now adding a valve or better yet, head pressure(less clogging issues with small orifices) can tweak that down to much less.
Whatever amount you really want.
You can also use a larger adapter for the tubing, but you still have the small pump part that's the constriction/clog point.
However, some simple things get around the issues of funk in the lines or rot of the traces.
This is really old news about dealing with fungus etc:
# Put your traces in a dark brown or opaque bottle (I use well rinsed glass cough syrup bottles). Light can destablize chelates.
Refrigerate stock (mark it well so someone doesn't take a swig) and leave a small 25ml bottle by the aquarium for convenience.
Since dry ingredients are more stable, only mix up a month's worth of PMDD at a time. Kevin Conlin adds a little HCL to the brew; (about 0.8ml 9M HCl/500ml). SeaChem acid buffer also or H3PO4 can be added to stop fungus(it hates really acid conditions....as well as bacteria, think peat acid bogs). Excel also will work pretty well, but dose not last that long, it will not oxidize anything at least.
Should help out a lot no matter what auto dosing routine you want to use.