I thought the weld-pak 100 was only DC output...

Not a professional welder, but I've got probably a couple hundred hours plus under my belt in your same situation basically teaching myself. It's a skill every man should know at least the very basics of. As others have mentioned youtube has lots of great info on many channels. Weld.com is a good one.

I agree it looks like you probably need to go a little hotter. I have two little Champion flux core rigs and don't they spatter that much normally.

Also as far as technique goes, when Mig welding the cursive E or Christmas Tree drag works pretty well for me with a little practice.

It takes time in the saddle and working with lots of different materials and gauges to get a good feel for it. You should get some scrap to run beads on so you can experiment and have side by side comparisons of what happens when you change something up.

Need to get the Lincoln MIG at the ranch refurbished. And get some practice! Only did stick in HS and sold my 220 stick welder yrs ago. GK thought about welding school but went electrician now. Shame as they got lots of welders at the Grapeland plant, probably could find somebody to teach him..

To the OP - KUDOS.