It's possible that this is just a sleep regression - you yourself mentioned the "eight month crisis" (sometimes known as the 9 month sleep regression, but the timing varies by kid) which is a common time for bad sleep. With these "the only way out is through;" it's quite possible that no matter what you do the wakings will continue until the underlying cause (developmental leap, new skill, etc.) is over. According to The Wonder Weeks separation anxiety may hit just before 7 months causing fussiness, and Wonder Week 37 with its associated fussy phase is right during 7 months.
The book Bed Timing would suggest that 7 months should be before separation anxiety begins and that it is actually an ideal time for some form of sleep training. The book also makes a great point that no form of sleep training has been proven more effective than any other - the key is consistency in all methods. So if you are comfortable with a form of crying - whether it is total extinction or gradual waiting - this may be a good time to try. However the timing in Bed Timing contradicts the timing in The Wonder Weeks, so based on your child you'll want to decide whether now is a good time to sleep train. Based on what you're seeing I'd guess that the developmental leaps Bed Timing attributes to 8 months are happening early in your son and you may just need to soldier through until a happier phase, when you can begin to address any sleep issues that remain. Or you can try to address them now - depending on your child they may work despite the developmental issues.
It's also possible that your baby became overtired at some point - did you go on vacation or change your routine somehow? Being overtired tends to lead to more night wakings. Consider trying an earlier bedtime for several days and see if sleep improves. Just slide it 20 minutes for 4 or so days. If it gets better you may want to try even earlier. Make sure naps are in order as much as you can, too.