i'm going to say something you're probably also tired of hearing, because it's in line with numbers 2 and 3, but all i can tell you is: it's true. and that is:
if you're asking yourself these questions, and trying to make it make sense mathematically while feeling intuitively that it DOESN'T make sense, then... the problem is likely, and simply, that he's not THE guy.
you can stop reading there, but if you're inclined for story time, let me tell you a few stories.
friend one was never going to get married, and NEVER wanted kids. she knew that by 16 and she never wavered. she was so NOT interested in the whole thing that she didn't even let guys become more than booty calls. she had a few of those ('a girl has needs,' she'd tell me), but that whole bourgeoisie thing was not her bag, and was never going to be her bag, and every single person who knew her knew she wasn't full of shit. her booty calls were just penises attached to skeletons, frankly, and she'd laugh at that description because it was so true.
then, at 38, she met A Guy. in VEGAS, of all places. long story short, they eloped four months later. married 'for real' two months after that. and on their 'wedding' night, she got pregnant. with twins. now, 3.5 years later, she's a stay at home mom (she OWNED HER OWN BUSINESS, and sold it), and she loves it.
i only tell this story to illustrate that yeah, when you know, you know. i could tell more like that, but she's my best example, apart from myself.
as for the whole 'i need to have babies because i'm long in the tooth at 26,' i will goodnaturedly laugh at that. you have plenty of time. if you don't want kids right now, GREAT. if you prefer to adopt, that's also great. there's no need to base a decision about getting married on your uterus, because trust me, you've got a lot of good years left (more than 10, i can anecdotally assure you), and if you prefer to adopt anyway, so mch the better.
re the good sex thing, it's interesting to me that you pointed out your friends are mentioning this. that indicates you've been telling them your sex is... yawn-worthy. and while mindblowing sex doesn't always guarantee happily ever after (and fades even if it starts that way), if your sex is boring after merely a year, then... i'm kinda with everyone else on that. i mean, if you're content to settle, that's cool, but the fact that you feel the need to JUSTIFY it, and add all this other shit, indicates to me you aren't sold, and it doesn't feel right to you, but you feel some sort of onus to be 'above' what your nether regions long for. and that ISN'T necessarily a great start to a long term relationship.
all in all, if you're content with your relationship for what it is and resent others telling you what it SHOULD be at your 'advanced age,' i'm 1000% with you. i completely agree. you do you.
all i'm trying to say is, if you don't think he's 'the one', he probably isn't.