It seems to me that there are two different problems happening here:
- A problem of tone, in that you feel it's rude not to use
- A problem of timing, in jumping to the front and then demanding action before anyone can reasonably respond on their own
I think you would do well to break these apart and deal with them separately, because at least from my end, the timing problem sounds way more obnoxious than failing to use proper nouns, yet you sound more hung up on the name thing.
I'm assuming the memory issue he's referring to here is being unable to come up with character names on the fly, so he's resorting to indirect references like "someone who can heal" rather than a name. Or maybe he's saying he can't remember who can do what in the group, so he just makes a vague course-of-action suggestion and lets the players figure out who can actually accomplish that.
Either way, it comes off as passive-aggressive prodding rather than a direct request to another character, but he seems to be indicating that it wasn't intended that way.
If it's just that, then I would think this something you either have to live with and just learn not to take offense at, or (if more group members than just you find it obnoxious), perhaps you can find an alternative, like referring to others by class rather than name.
One of the players in my regular gaming group can't remember character names to save her life, so we've just gotten used to her calling the other characters "the wizard" and "the dwarf" and so on (the alternative being several seconds of "uhhh--" while she looks at her notes to remember what our names are). It's not great, but it's not terribly obnoxious, and we work around it.
This is the one that sounds to me like a legitimate issue. He's rushing into every situation to be the first to make contact and then commanding others without letting them have the time to come up with an answer on their own.
This comes off to me as a very "CRPG" way of playing: It's solo gaming, where your party members are just skills and spells with legs, there to do your bidding. Or possibly it's out of fear of being left out; by always being first in line, he guarantees that he won't be the quiet one in the back who never gets to do anything.
I would hope this is a thing that could be addressed by asking him to simply wait a little while and let other people proactively respond before he starts telling everyone what to do. That might work. But it might not. While I don't like to toss these terms around haphazardly or diagnose third-hand, I will say that I have a family member who is on the autism spectrum, and reading your description of this behavior, all I could think was that it sounded exactly like the way he acts sometimes.
How to discuss it
My suggestion is to talk this out, but you're going to need to be very careful of a few things.
Be careful to focus on only one problem, and focus on the problem, not the player. "When you do this, it makes me feel that" is a much more productive way to discuss the issue you're having than "You're annoying when you do this".
For example, "When you immediately start telling the group what to do, it makes me feel like you don't trust me to come up with ideas on my own, and I don't have fun because I feel like you're telling me how to play my character, especially when you're telling me to do something that I was going to do anyway."
If it were me, what I'd do -- and I'm not claiming to be perfect, this is just what I'd do -- is to first talk to one or more of the other players, in private, and check my perceptions. If this behavior bothers them too, then I have a good basis to think this is a real problem and not just me having a weird hang-up. If they don't think it's a big deal, then maybe the problem is me rather than the other player.
Then I'd talk to the player in private (again). Don't let on that you have discussed it with the rest of the group -- never, ever say things like "Well I talked to the group and they all agree with me" unless you really want to come off like a jerk. Speak only for yourself.
Be careful not to push your point too hard. Lay out your position, and back off. Your instinct will be to get a resolution: an apology, a promise to do better, whatever. But that instinct is wrong. People often get defensive when you're telling them they've done something wrong, and they'll refuse to agree with you just because of pride. The harder you push, the more you raise the stakes, the more they'll want to avoid being seen as "giving in". But if you say your piece and leave it at that, often the person will take that statement to heart and strive to do better in the future, even if it doesn't sound like it at the moment.
If all else fails, bring it up with the DM. He may be able to use a few techniques to help with that behavior, like "going around the table" to ask what each person does, or even directly saying "Okay, hold on a second Jeff, I want to hear what the others want to do." Part of being a good DM is noticing when one person is constantly in the driver's seat and making a conscious effort to give others the first crack at talking.
Leaving the game is a last resort. I wouldn't do that unless everyone else seems united in being totally unbothered by the behavior, but if it really is a problem for you and everyone really does seem to think you're the one being silly, then you may not have a good option. (It may be worth it to look up the Geek Social Fallacies, if you aren't aware of them; many gaming tables have been poisoned by those toxic behaviors, allowing one bad player to ruin the whole game.)