I had trouble with DD with latch/feeding too. From day 7 I had her on formula and breastfeeding. I did stick to breastfeeding still though and breastpumped and she still takes breast at night now and pumped stuff half the day at 8 months, so am pretty proud of myself for that, I must confess but it was really, really difficult.
I doubt I could've done it without the support of my family as lame as it sounds, it's very true because they could take DD when I was pumping, whereas if it was just me and DD then that wouldn't have been possible when she was so small.
I know for a fact though stress can halt production of breastmilk and it sounds like you had a lot of stress going on at this time and understandably so. As best you can, try and see this pregnancy as a completely different experience than the previous one and equally, what happens next.
1). Will your baby feed constantly? Maybe, maybe not. Honestly, every baby is different. I know someone whose newborn fed every 4 hours, DD was around every 2 hours and then went to every hour and I even know someone who was feeding every 30 minutes. I fed very regularly for my mother apparently, but my sister fed a lot less often and we are from the same mother, so they are very different.
2). Read up on different positions as much as you can - there are many breastfeeding positions, some suit different people more than others. I'd also read up on how to do the basic latch - align the babies nose with your aerola and make sure most but not all of it is inside your babies mouth (aerola not nipple) if I remember correctly. If you are really worried, you could go to a breastfeeding counselor before the baby arrives. Also consider having extra help with your latch when your baby is born from midwife team/hv/breastfeeding counselor etc. I know people say it's easy but it isn't just easy for everyone. Chances are it was your baby struggling, not you but you will never know and it's OK, because no harm has been done. If as you say there isn't a great support network try outside your area a bit for groups/advice.
- Preparing really is doing what you are doing now. Researching, learning and dealing with any issues you feel may arise. Just don't let it consume you.
I know it sounds easier said than done but just enjoy your pregnancy and your baby. The more relaxed you are, the more relaxed your baby is and the more of those relaxin and oxytocin hormones will flood you and your baby and you will feed blissfully.
But you are doing what you can.
I wish you the best of luck with this pregnancy and breastfeeding afterwards. :)