That looks a lot like the Horizon Hulk kit, but I could be wrong.
The hollow material screams vinyl to me as well. Most of the super hero kits were casted in vinyl.
After reading the WIP, I can say you're doing a better job of fixing the Hulk than the original modeler did assembling it. Most modelers who do vinyl almost always fill the kits with plaster so I find it odd that the original modeler didn't do that. It looks to me like he was cheaping out on materials so he could keep an extra few bucks in his pocket. If that kit was filled before shipping, I can almost guarantee that those breaks wouldn't have occured.
I can also tell that from the looks of the original paint job, he would have had to have used Model Master acrylics. They're the only paint I know of that can get that kind of finish. It's also important to note that vinyl parts will ONLY accept acrylic paint. Everything else won't dry no matter what you do.
I'm also liking your paint job a lot more. I find your colors to be more in tune with the comic instead of the movie. The original paint scheme just didn't fit the sculpt if you ask me.
Overall, great work so far. I look forward to seeing this finished and I also look forward to seeing future figure kits from you. BTW, I'm a fan of your other works.