As someone who burns wire every day for a living, i will say this.
Would i weld my axle with flux core....
Yes and no.
No beacuse i have a bad *** machine at the shop.
Yes beacuse if that sucker broke and i was out in the woods with a stack of batteries and a welding lead, i would weld it it with a dam stick lead and a coat hanger if i had to and i bet it would work....
Just keep going.
Clean, clean clean and clean again.
Clean the ground clamp, clean everything.
Good job man! You got the right attitude, you will get it right.