You should have enough room on a Dodge boxside, behind the brace, to push with a rod or PDR tool (which I assume you don’t have since it’s your first time but you can make one). Get all the paint off, use a grinder with a flap disc or something so you don’t grind through so that you can put a stud anywhere you want. Take your taillight out before you hit it with sand paper and say bad words :-). The top looks good, if you can start to push the bottom from the back, you should be able to use the studs to finesse it before filler. you can warm it with a heat gun before you start to push and that sometimes will help it move a little easier. Keep going!!
How can I pull that panel outwards?
Get all of that paint off of there so you can see what you’re doing. After you weld some studs on, you can warm up the panel with a propane torch or oxy/acetylene if you have it. Start at the bottom and get the round bodyline first and then straighten the crease. Heating it will help the metal move easier without tearing from slide hammer blows.