If you are not getting sparks at all, the frizzen was not hardened. If you don't own a small propane gas torch, then find a local machine shop, ask them to heat the frizzen up to Red hot, and quench it in oil. Then, use a wire brush, or power tool to get the scale off the frizzen, and heat it to 450 degrees in your oven for two hours, and let it cool down overnight. It should spark just fine.
To set the flint, you should open the frizzen, and lower the hammer so you can see where the bottom edge of the flint is pointing in the frizzenpan. It should point to the center, or just forward of the center of the pan with a new flint properly positioned. Then cock the hammer back to the half cock notch, and close the frizzen. It should strike from the center to the bottom third of the frizzen. The frizzen should flip open completely when it is struck.
Make sure the frizzen pivots freely. The feather spring only needs to keep the frizzen closed when the gun is held upside down. Any more weight than that simply causes problems with crushing the edges of your flints and wearing them out sooner. Polish the contact point where the toe of the frizzen meets the top arm of the v-spring mirror smooth. You can use emery papers in ever smaller grits, a dremel tool with fine stones and then papers, or emery stones you get from a gunsmithing supply house, like Brownell's. If you have a small ceramic stone for sharpening knives, you may be able to use this to polish the surfaces, if it is fine enough.
Test the strength of the feather spring by using a trigger pull gauge- ask around to see if someone already has one they can let you use- and hook the arm of the gauge over the top of the frizzen and pull slowly forward until the frizzen snaps open. More than 3 lbs is totally unnecessary.
Make sure the side of the v-spring is not dragging against the lock plate. If it is, grind the side of the spring to eliminate the part that is touching. Measure the spring tension again. IF the spring is too strong, then reduce the spring tension by slowly grinding away metal on the outside of the arm of the spring, and if there is a lot of metal at the bottom of the "V", then grind away that so that the width of the metal at the bottom is the same as the width of the two arms of the "V" at the juncture. Keep water handy to cool the spring so you don't remove the temper, or soften it. Hold it in your hand when you are grinding so your fingers will tell you when it is getting too hot! Reduce the sides of the upper arm of the spring until the tension get to that 3lb. weigh or slightly less. Then reassemble the lock. Try the frizzen to see how well it snaps open.
If the mainspring is putting a lot of tension on the cock, or hammer, you should do to the mainspring what you did to the feather spring. Most of these spring are well over 20 lbs. You will have to rest the gun on a bathroom scale, take a starting reading for the weight of the gun, and watch the scale while you cock the hammer back. The highest reading on the scale should be recorded. Then subtract the beginning reading and you will have the mainspring tension in lbs. Unless you are shooting a Brown Bess, or another musket that uses the very large flints, you should do well with a mainspring that has only 10 lbs. in tension. They do work if the lock is set up correctly, and flint are set in the cock properly. However, you will probably want to stop and try out the gun when you get the spring down to 20 lbs. It will still work better than what you got from the factory. After you have shot it awhile, you may get the courage to take it down more.
Always check the lockplate on both inside and outside after you have shot the gun several times to see if there are any rub marks on the plate where something is rubbing against it. This is the visible evidence that something is not working properly, and causing the action to be slow. Remove the high spot, or burr, that is marking the place, and then polish the plate. Check it again several times to make sure that everything is moving freely.
If you are going to use leather instead of lead to wrap your flints, use rawhide, and not that tanned leather like is shown. Tanned leather is too soft, and creates a shock absorber that lets the edge of the flint bounce on the frizzen face instead of cutting a clean slice of metal from it to throw into the pan. The edge then loads with bits of steel, and finally dulls and won't spark because the cutting edge of the flint is physically being blocked by the metal chips in the edge. Then you have to knapp a new edge, which throws away expensive flint. My flints in my .50 ca. rifle routinely give me 60-80 strikes per flint. I sometimes do better than that. I don't have to knapp, and I don't ever worry about the gun going off.