Is this a 3310 or variant? Did you buy it new? Other than the secondary metering block and the primary jet, have you done any more fiddling with it? If it's a used or older carburetor, is it really clean? Does it have the proper gaskets?
A 68 primary jet is too small for a 750. Go back to the 72. Put the AFR meter away. It's not helping you. Tune the carburetor to make the engine run good regardless of what the meter says. Once everything is well, hook up your meter to see what the engine likes, write that down, and put the meter back in the box.
Forget this being a bleed problem. Unless they are replaceable and someone fiddled with the carburetor before you got it, the bleeds should be fine to keep you on the road. Not perfect, but not the source of your problem.
Check your primary and secondary throttle blades to make sure you are not over-exposing the transfer slot. What can happen in achieving your 700rpm idle is that the secondary throttle could be completely closed, and the primary open too far and exposing too much of the transfer slot. That detail will make sure your idle and tip-in response is working correctly.
Just so you know, if you have a really stinky exhaust...you know, eyes watering, runs you out of the garage...that is raw fuel -hydrocarbons. You get that from a lean condition where the fuel doesn't fully combust or you get a lean misfire. It can also be an ignition misfire, but in your case, you are running too lean. A rich mixture doesn't have that smell. And other than really poor fuel economy and short plug life, with a rich mixture the engine will start fine and run okay. Not perfect, but it won't be giving you a lot of problems. This is why it's better to have an engine on the rich side, than lean. Particularly at idle.