The "foot thing" could be any number of things, he could have been trying to step on top of Pumpkin, he could have been wanting to use his foot to grab-onto Pumpkin so he could bite him, it could have been a defensive/protective gesture, or it could just have been an unconscious movement that he did while trying to bite/attack Pumpkin and wasn't even aware of...Either way he is obviously the aggressor in the situation, and that makes sense since he was there first, and as far as he's concerned it's "his house", you are "his person/people", and it's not at all uncommon for a bird who has been the only bird for some time to act this way whenever a new bird is brought into their territory, as they are extremely territorial and protective of things and people they are bonded to...
There is no way to know if their relationship will ever improve as times goes by, but chances are that they aren't ever going to be "friends". It might happen sometime down the road, but doubtful. It's most-likely all up to Pampa, as he is the aggressor and the dominant bird, and the one who's territory has been invaded. If Pumpkin responds to Pampa's aggression in an equally aggressive way, it's most-likely just as a defense and not because Pumpkin wants to actively attack Pampa; however, it's equally possible that if Pampa had accepted Pumpkin into his "flock"/territory from the start that Pumpkin may have not accepted this anyway, but as it worked out, Pampa is defending his territory and protecting his people from this new bird that he is not accepting...
There is never any way to know how two birds are going to react to each other, or how they are going to get along. They are very much like people in the way they form relationships and bond with other birds, or the way that they don't...Probably what you're best-case scenario is going to be is that someday Pampa stops being actively aggressive and accepts Pumpkin as a member of the "flock" and simply tolerates Pumpkin being there and interacting with you and living in his territory...but it's unlikely that he is ever going to be "friends" with Pumpkin...
I first brought home Lita, my Quaker parrot, at 11 weeks old, and she was the only bird in the house except for my 8 Budgies who live in a walk-in aviary and have separate out-of-cage-time each day with me than she did (the bigger birds don't interact at all with the Budgies)...So then I decided to bring home Duff, my female Cockatiel, when she was just 8 weeks old (fully weaned but just a tiny baby), who is the sweetest bird I've ever known in 33 years of owning/breeding birds. She's just the most docile, sweet little bird that wants nothing more than to get scratches from everyone she meets, she accepts all people, she has never bitten anyone even once nor attempted to, she lower her head for everyone automatically upon meeting them so they can give her scritches and she is just the most well-socialized, sweetest little thing in the world...and boy did Lita hate her with a passion!!! Lita actively tried to attack her every chance she got, and she would bite me if she was on my shoulder and I would even say the name "Duff"! It's the only time Lita ever bites me, when I touch Duff or say her name in Lita's presence, and poor Lita wanted so much to get Lita to preen her, it was sad...but that's just the way Lita is with her to this day...So then I brought home Bowie, my Green Cheek Conure, about a year later when he was 13 weeks old...And they took to each other right away, bonded pretty closely with each other, and Lita had absolutely no problem accepting Bowie into her house. To this day over 2 years later they play together each day, they snuggle with me/on me at night together with no jealousy issues, and they rarely have any fights or any problems at all, and are the only two birds I have no problem letting out together unsupervised.
So there is absolutely no rhyme or reason as to why birds accept other birds or people and others they hate and are aggressive with from the moment they set eyes on them...I've gotten Lita to the point that she now won't bite Duff because she knows she'll get a "time-out" and she won't get her treats for that night, what she does now if she happens to be able to get near Duff is she'll simply fly right to her and chase her off of wherever she's sitting, as if to make sure that Duff knows "I'm still the boss, this is still my territory, and even though I can't bite you or attack you anymore you're still not allowed to be on my territory when I'm around!" So I know they'll never be friends and I cannot ever trust them to be alone together unsupervised, but Lita can be in the same room with her out free if I'm there and she won't attack...but that's the best I can hope for...
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