Slugs should not create any more trouble than any other loads with concern to the choke tubes. Try a different choke tube wrench. The stock wrenches with most guns are just OK at the job. Some are down right poor. Stamped metal with little hand grip area for leverage. There are several great aftermarket wrenches available that offer better grip for your hand and more positive attachment to the the tube. You may want to also apply some penatrating oil to the tube and let it sit overnight.
I have had some stuck tubes over the years and did have to really work to get them loose. Carlson's makes one for about $20 that expands inside the bore to grip the tube. I have one to this that works well on most stuck tubes. Just make sure any oil is cleaned off the bore surface before you try to remove the tube. When installing your tube don't over tighten. Snug works just fine.
If all else fails take it to a gunsmith. Better to pay $30 to have them take it out for you then buy a new barrel because you bugger your up.
Good Luck
APEXDUCK
I have had some stuck tubes over the years and did have to really work to get them loose. Carlson's makes one for about $20 that expands inside the bore to grip the tube. I have one to this that works well on most stuck tubes. Just make sure any oil is cleaned off the bore surface before you try to remove the tube. When installing your tube don't over tighten. Snug works just fine.
If all else fails take it to a gunsmith. Better to pay $30 to have them take it out for you then buy a new barrel because you bugger your up.
Good Luck
APEXDUCK