Honestly, if you make your way with your lifestyle, I think you should keep at it, and find a girlfriend who is more suited to your personality (and one whose dad doesn’t add pressure on the pile).
The corporate world is a shallow scum sucking abyss of malcontent and bullshit. Happiness is really not found there, at least that was my experience. I am way way more happier living a lifestyle similar to yours now than I was living a high paying lifestyle and I doubt I will ever go back to city living. Maybe my experience resonated more because I am an artist too – when I saw all my hours and energy being drained away to profit a big company doing ethically dubious business, it killed me, literally. Pieces of my soul were flaking away rapidly. Worst of all was coming home at the end of the day and having only enough energy to regret not being able to heavily pursue artistic endeavors before going to sleep and waking up and doing the exact same shitty day over and over and over again.
Beyond this one instance though – if she pressures you on this, what else will she pressure you on? You are in your 40s so being a dad can be a bit more challenging, I would really hope she wouldn’t pressure you into this, but she could try depending on her age. However I think it’s a bit naive to think that she will stop pressuring you to conform into the mold she and her father fit into just because you get a job. I think it will be more likely that the pressure will change to ‘encouraging’ you to work harder, trading in your tools for a minivan and diapers.
And keep your hair long! Fuck those who want you to cut it. You do what you want and love to do in your life. Those who express discontent at your way of life and happiness are only unhappy at the fact that you are content in your spot whereas they are not despite ‘having so much more’ or ‘being in a better place’ or whatever other bullshit they’ve been brainwashed into believing.
So I think this clash between you and your girlfriend can be used as a way for you to determine what you want to do in your life, and whether your girlfriend and her dad will help or hinder your goals. If your girlfriend wants to raise a big family, and you do as well, then you might have to sacrifice part of your creative energy in order to gain more financial stability. Or you can pursue your art harder and become more successful in it. But if you love your art or your current way of life more than the thought of creating a family, then it is in no way wrong to admit that and to let that reality extend over into you and your girlfriend’s relationship as a whole.
As for me, I am extremely content in my current position. I have no desire for children or marriage and neither does my man-mate. We don’t need lots of money to get by, nor do we subscribe to the city-living thought of working for someone else doing something you do not love to do in order to get money which you then use to support yourself. We have chosen to cut the middlemen out of this and work to support ourselves directly. Certainly one of us will need to get part-time jobs to bring in some consistent money, because even out here in rural-land there are bills and mortgages and crops don’t grow all year long to fund them, but at least we won’t be forced to take on a full-time career job, because we simply don’t need this type of income in exchange for the price it takes from your soul. However, me and my man-mate communicate very often about our desires and wants in our lives, and based on your posts I am not sure if you have this level of communication with your girlfriend. I find without this level of communication any serious lifelong relationship is pretty much impossible to handle.