Put a 1/2 in drive deepwell socket under the flange. It should be long enough for the stud to be pounded all the way in. If not then cut a piece of sturdy pipe long enough. You can also use a press this way too if you have access to one.
My sons 99 had vibration problems he assumed was death wobble and kept driving. Turned out a wheel stud had sheared off and as he kept driving two more came off. When he stopped the wheel was barely hanging on by two studs that were next to each other. Another mile and it would have been bad. I was able to get the old studs out with PB Blaster and a standard household hammer. I put the new ones in by simply placing a large nut over the stud then I put the lugnut on and tightened it with the lugwrench until it was seated. Repeated two more times. Then I took off the lugnut and put the drum back on and all was good. I can't imagine having to use an impact. Just some good elbow grease and a strong back will do the trick. And I did this with the axle in place, all I did was remove the drum. This was all done on the side of the road in about an hour and I'm no mechanic.
I could not hammer them in. I had to use a friends impact running 130 psi to get them in and that almost did not do it.
Sounds like you might not have had the splines of the stud aligned properly with the grooves in the hole. Yeah its tight, but the only thing imo that should have made it that hard to go in would be misalignment of the splines.