If you are planning to live as a man with breasts and reshaped nether regions, you might also find it valuable to check out the the trans male section of the forums, as there are men there who are coping with similar challenges. (They are, of course, men, and you are not. But there's a lot of helpful advice relating to "how to use a urinal with a urethra that doesn't run through the penis," etc.) What you want is as valid as any other way of being trans, but a cis society who doesn't understand the complexities is going to give you more complications to deal with than the "traditional" trans woman whose narrative fits what they expect.
I'm also going to chime in to support the idea that hiding things from your wife is a BAD idea. My own wife is active in trans partner support communities and has been for years, and one of the biggest reasons that marriages break up is a sense of "betrayal" and being lied to. Some partners can accept "I have been terrified to admit this to myself so I also hid it from you," but "I started HRT and didn't tell you for months" is very often a dealbreaker.
(I had penile inversion GRS a few years ago.)
1. When I have a SRS (PI), how does everything feel, just normally? For example, when I want, I can pulsate my penis, when you do that as a POST SRS MTF, can you do the same, but what does it do when you do that? It feels like it comes from the prostate.
I'm not sure what you mean here. If I clench the muscles I use to stop peeing, however, I can tighten and bear down with my vagina (basically, Kegels, and this is how it works for cis women too).
2. When you sit down, and its finally gone, do you feel different? Do you feel like its missing, do you even notice?
It feels different, but in a good way; everything is smooth and nothing is flopping around or getting in the way of sitting. However, I do sit directly on my vulva now, which felt weird at first.

No way to move any of it out of the way!
3. Can you concentrate more on work than ever before?
I guess? Honestly, it's been so long since GRS that I assume dysphoria was a big distraction then, but I don't actually remember what it was like.
4. Do you still live a heterosexual life with a female? How is sex like now, and do you do anything different than before, i.e., toys, positions, etc...
Well, I live as a lesbian with my wife. Not sure what you mean by a "heterosexual life," unless it's presenting male in public (NO) or having penetrative sex (sometimes). We have sex the way lesbians typically do (yes, that can include toys).
5. Even with minimal HRT, do you still have significant breast growth? How big? And how do you hide it?
I have been on a super low dose of HRT from the beginning; I am now 38DDD. I can't hide it, and couldn't since I was a C cup at 3 months in.
By six months, I also couldn't pass as a guy even with male clothes, male name, male ID, and insisting I was male (to vote).
6. Have you gone back to testosterone? How has it affected you? Or how do you think that it would affect me?
NEVER. I'm afraid I have no idea how it might affect you, but you want to consider this part very seriously if you're planning to have your natural hormone factories removed. You will need *some* kind of hormones for life.
7. Now that its gone, has it affected you in any negative way, do you miss it? And what do you miss about it?
I occasionally miss peeing standing up in the woods on a long hike, but there are doohickeys made for cis women that I could try (and I might). Other than that, no, no negatives and nothing I miss.
8. How are the possible toys, and masturbation? Does it feel the same as it is now?
I assume by "is now" you mean "with a penis"? I have a vibrator and enjoy using that; stimulation does not feel the same as it did before, and the effort and tricks I need to enjoy sex are very different now. For one thing, it's a lot easier to get distracted or bored and give up! Orgasms are better, but a lot more work to achieve (which seems normal, from the women I've been with).
9. Do you get erect, is it the same feeling as it was when you were male? And what exactly gets erect when you do?
It's a little bit similar, in that it feels like that "tingling" sensation I used to get when my penis was about to become fully erect. The only thing that does become erect now is the clitoris, and subtly. I have heard from many cis women that the feeling is what it's like for them too, and clit erections are typical for cis women.
I actually do agree that therapy might be wise - you'll have to choose a therapist carefully to find one who accepts non-binary identities and/or lifestyles, but it could help you untangle some of what you're thinking about. For one thing, the focus on sex post-op feels a little weird to me, as that's about 1% of my existence now (I spend more time worrying about peeing with a vulva, to this day, than about sex). I'm not saying *you're* weird or bad for thinking that way, to be clear, just that you might be surprised by how little it matters compared to daily life with a vulva - like remembering to wipe properly, the bizarre feeling of crotch sweat getting caught in all those folds, etc.