Sorry it took me longer to finish what I was doing, here is my explanation on the 9 upgrades.
Note: Danny Phantom's Island level is 39 Gigatons.
When Technus merges with Technology, he base becomes considerably stronger due to him taking in said power as well. This is shown in season 2, episode 8 "Identity Crisis", in which Technus merges with The Fenton Ghost Assault Vehicle and a ton of other technology and becomes Battlesuit Suit 2.0. When Technus is removed from this battlesuit, his physical appearance is altered and he receives a larger upgrade shown in season 2 episode 12 "Flirting With Disaster", in which Technus 2.0 defeats Danny and states Danny was foolish to pick a fight with him in his upgraded form.
Note that Technus has to do this multiple times before he fully evolves into his next .0 state. In season 1, episode 4 "Attack of the Killer Garage Sale" Technus merge with Technology from across Amity Park and got boosted to the point where he no sold a barrage of punches from Danny, in season 1, episode 12 "Teacher of the Year", Technus created another Battlesuit and then gained more power while in the Doomed video game. Then in season 2, episode 8 "Identity Crisis", Technus merges with enough technology to become 2.0.
Consider he could stomp people around his level before fully evolving, it means each .0 version is strong enough to stomp the later. So Technus and Skulker individually are comparable to Danny who is At least Island level, likely Island level+. Then the two fused which would make them stronger, then they go through Skulktech 2.0, 3.0, and so on until they reach 9.9... so basically, Skulktech 9.9 stomps 8.0 who stomps 7.0 and so on down the line until you reach base Skulker and Technus who are At least Island level, likely Island+.
It's far beyond a 2 times gap so yeah Skulktech 9.9 should be At least Island level+. He also beat Danny fairly easily, and this would support Dan being just that much stronger since Skulktech 9.9 stated Danny was much weaker than Dan.