Lightening the spring tension yourself is the problem here. There needs to be a perfect balance between the weight of the hammer and the tension of the spring. If you reduce the tension on the spring and do nothing with the hammer, what you end up is a hammer that doesn't have enough momentum for a proper primer strike when you fire. If you take a look at some match-grade triggers for sale online, a lot of them will have the hook of the hammer cut into a rectangle to accommodate the lighter spring tension. That said, you could possibly cut the hook off the rear of the hammer yourself to remedy your light primer strikes with the spring tension you currently have, but replacing ruined hammers costs a little bit more than ruined springs. I personally just cleaned up the sear on the trigger with some light polish and a dremel buffing wheel and installed J&P 3.5lb springs. It runs perfectly for me with Federal Bulk ammo.

If you end up getting serious with your trigger though, you're just better off buying a drop-in that works like a Rock Rivers Arms 2-stage or a Timney single stage. If this rifle is a SHTF gun for you and you want something combat worthy and reliable, get a Geissele and never look back.