Hey CT, welcome to the DhO.
I'm a father, partner, home-owner and all 'round normal guy with a job so I can tell you quite confidently that it's possible to do what you're asking about. And more. Not being able to go on retreat isn't a big deal, it'd be useful and an amazing opportunity to practice solidly for the entire time but it's not required to get into jhana, or even to get stream entry and beyond. I know 'cause I've done it, as have loads of people in similar situations to yourself, some of whom also post on here and will hopefully offer some advice along the way.
How to increase mindfulness through the day? The first thing to remember is that every time you realize that you're
not mindful, you actually
are being mindful because you've just recognized the absence of mindfulness. Straight away, you're onto a winner here because that's a feedback system in itself; you're mindful and calmly attentive to what's happening
right here and now, then you get distracted by something and go off on the thought train following the inner narrative as it plays out...then you realize you weren't being mindful and immediately you're back to being aware of what's happening
right here and now!
Don't beat yourself up if you get distracted, it happens and it's done. No point in pursuing it around your mind, you won't catch it because it'll just vanish back to the emptiness it arose from, let it go and go back to being mindful, attentive to what's going on and enjoying this moment as it is.
To increase concentration, nothing beats a regular meditation practice done daily for as long as you're able to, even if it's only half an hour it's better than no practice at all. Off the cushion, there are lots of ways you can practice concentration creatively during daily life, the best foundation practice is simple breath counting in cycles from 1-10, returning to 1 if you loose count or get distracted. Stay with as much of the entire breath as you can, follow the whole of the inhale and the exhale, again if you get distracted it's no big deal, just go back to the breath again and you're back in business.
Another great concentration practice is "kasinas", which are various objects on which the attention can be fixed. A simple and easy to obtain example is a plain coloured bowl, prop it against a wall and focus on it as intently, actively and as engaged as possible. Again, if you wander off, just come back to it. Bring the attention back in the way you'd bring a puppy over it's water bowl, pick it up gently and place it with your object, whether that's the breath, a bowl, a candle, the whole body, the whole sensate field, whatever. It's that simple, really. It's a bit more subtle as you go along but the basics are the same and these examples are tried and tested.
How long it would take you to access jhana depends on a lot of things, but in general it's really not
that difficult if you're willing to put in the work to get there. I'll post a few links for you which may be of use, hopefully the advice so far is of use to you but feel free to ask anything you like. Get a practice going, that's the most important thing, even if you need to get up half an hour early it's worth every second, even if it doesn't seem that way sometimes.
Best of luck and welcome on board.
The Hamilton ProjectA site by some dharma buddies who also frequent this site, full of great practical advice and bullshit-free information about the nuts and bolts of practice.
My blog with an article on access concentration which may be of use to you.