There's a lot of unmentioned rules-of-thumb being applied here.
One of the old rules is/was: "Twist rates faster than 1:48 have accuracy problems with patched round ball and large powder loads." A lot of folks go further, saying, "A slower twist rate [slower than 1:48] is better for a patched round ball when using large powder loads". A corollary rule is "Conical bullets don't shoot well from slow twist barrels [slower than 1:48]"
The "skipping" across lands and grooves problem, which is often cited as the reason for the above rule-of-thumb, is in reality a factor of very heavy hunting loads with a patched round ball in .54 caliber and larger. (source: The Sporting Rifle and Its Projectiles, by Forsyth) We're talking more in the 140 grain category, not the 70-90 grain range. Now it's true, a slower twist rate for a round ball barrel has advantages when one is not using very heavy loads....ease of loading, ease of loading more than one shot without swabbing, less torque on the shooter when using hunting loads, and quicker cleaning. (Source: Instruction for The Formation and Exercise of Volunteer Sharpshooters, Barber)
So for example 1:48 was for a long time called a compromise twist rate for both round ball and conicals, BUT we now know that a lot of rifles were made with that twist rate prior to the conical bullet becoming popular. Today, a Green Mountain barrel in .40 caliber is 1:56, BUT a Rice barrel or Colerain barrel in the same caliber only comes in 1:48. So the caliber appears to influence the twist rate choice too.
Further along those lines, the 1:24 twist rate on the Pedersoli Jaeger rifle is faster than on your rifle, BUT the recommended bullet is a PRB. Pedersoli also makes several rifles in a 1:72 twist rate that are repros of Civil War muskets...and they shoot conical minnie balls very well. So it may be more than simply the twist rate when it comes to accuracy in a particular rifle.
A rule of thumb that may benefit you is to begin with grains of powder equal to your caliber. So as suggested in some previous posts, reduce your load to 50 grains. Work up or down from there.
You need to try and shoot from a a good, solid rest, to really determine the accuracy, and you need to examine your patches after several shots. I prefer to shoot from a supported, sandbagged position on a bench.
I've not really seen the lube make that much of a difference, unless you are working for maximum accuracy for targets at say 100 yards, and the difference between a hit in the 9 ring or a 10 ring will be the difference between winning and going home empty handed. Others may disagree, but I've found the different lubes for me are more for ease of loading, and weather resistance, than accuracy, but I rarely do serious target shooting. For hunting, the difference between a "clover leaf" group and a 4" group at 100 yards won't matter to a Big Game animal.
The patches, the substance, the thickness, the method, and what happens after firing, will tell you a lot about what is happening if you don't have satisfactory groups. If they are destroyed, or burned through in spots, they may be too thin, or you may have sharp spots on your lands that are cutting the patches or both. Lube may help reduce this, but really your patches on a round ball should survive without holes even if you loaded a patched ball with a dry, cloth patch.
Part of the fun, in this game, is working to get the most out of your rifle (imho).
LD