Does he even have a tadpole and if so, why did we not connect with him. Someone pointed that out and I found that interesting.
Yes, he does. He gets tadpole powers, can use the tadpole in conversations, can be tested by ormellum and Ethel, etc. He has a tadpole the same as everyone else. He didn't do the brain connect upon first meeting, but you certainly can prod his thoughts at other times. There's no big mystery surrounding the lack of initial connection, unfortunately; there are two primary possibilities. The first is that it's an oversight or unintentional side effect of design (Gale wasn't initially intended to be in the first EA batch of characters... though in this situation, you'd expect them to have put something in by now probably). The other in universe possibility is that Gale has the most well-ordered and trained mind in the group - as an experienced wizard - and he actually just has better control of his tadpole when we first meet up, than the others do. If we try to pry into his mind at that point, he locks us out, even on a success, so he's being communicated as having strong mental faculties.
I'm just really curious why people who don't trust him don't - unlike practically everyone else, he never lies to us or deceives us. Saying that "he could" be lying about all of this and being manipulative is an empty argument because that's literally true of every single thing we see and hear from every single person, if you go that route. There is no indication that he's being in any way dishonest, and many indications that he is being truthful and forthright, throughout the EA... saying "Well you just don't know him yet" is equally empty - because we all know him as well each other, and are working off the same evidence. I've yet to see anyone put forward any actually substantive reason for why they think he's up to something or deceiving the party - or even any explanation of what made those people feel that way, and I'd really like to understand it, since there's quite literally nothing that I'm aware of in the game to see that points in that direction.
I know one of things someone pointed somewhere is Gale's knowledge of Netherese magic. Not to say he is well verse in that type of magic but in a conversation that I saw he kinda gives you the impression that he knows more than he's letting on. We know from Auntie Ethel that the tadpoles have been tampered with Netherese magic. Did Gale sense Netherese magic in his tadpole but didn't say anything to us? Which could be why he seems more in control of his tadpole and even able to block us out as you said. It's one of the reasons why I have mixed feeling about Gale. There seems to be something off about him. Nothing necessarily bad just off.