1. Snow Leopard runs fine in 2GB of RAM, though more would obviously be better if that's an option. It's a very cheap upgrade that makes a big difference.
2. Snow Leopard itself is five years old now, so you indicate that you're using an OS version (and thus equipment) from well before that. I'm glad it's been working well for you, but the whole thing about computers and OS versions is that you have to upgrade them periodically -- broadly speaking every five years or so -- in order to stay current with improved security and newer technology. This isn't a "forced upgrade" in more than your houseplants "force" you to water them from time to time.
3. You can order a Snow Leopard DVD from Apple that will update you to 10.6.8. It costs $20. I'm making the assumption that you've already checked to ensure that your machine will in fact run it (must be powered by an Intel processor). If so, installing Snow Leopard will allow you to work with your iPhone ... but you can safely expect the next iPhone will require a newer system and thus (in your case) a newer computer. Doesn't have to be brand new but apparently newer than what you currently have.
4. Get used to this. I'm writing this to you from a 2009 MacBook Pro, which I used to replace a 2007 MacBook that just couldn't be upgraded to handle the technology's direction to rely more heavily on the video chipset. This one is going to suffer the same fate and will need replacing later this year. Both were great machines for my purposes but the best time to replace a machine that's falling behind is BEFORE you get up the creek without a paddle, not well after.