Oh I definitely feel your pain! Unfortunately I don't think you can do much at this age - three months is so young and they are barely getting used to the world. A few thoughts:
1. It's possible he's going through a growth spurt and will start to give you longer stretches after he's through it.
2. your best option, at least temporarily, might be to go to bed as soon as you can after he does so you can get some solid sleep. I know it's not ideal but at least you'd get a good 4 hrs if you went to sleep at 8.
3. You could put him to bed later to shift the 6 hrs to a more palatable chunk of sleep for you. When my LO was that young we put her in around 9 a lot as that worked better for us. As she got older we shifted bedtime earlier, now it's 7:30.
4. You need to make sure he is getting enough sleep all day - counter-intuitively, good naps beget good nighttime sleep and vice versa. I really liked what the "baby whisperer solves all your problems" said about this (tracy hogg). This is the age where you can start to make sure he's got a good routine during the day with eating, sleeping and activity.
5. I would stick with the dream feed - when we first started it it didn't seem to help but then it did. In addition, I would try "tanking him up" before bed time - that is feeding him as much as possible in the 3 hrs or so before bed.
That's all I can think of - I do wish you you the best of luck. It is so hard to go back to work between the sleep deprivation and worrying about the little one.
Good luck!