I'll offer the following, with the assumption that your bike is already in (at least) relatively good shape mechanically (e.g., driveshaft splines are well lubed, and tires are at least fair, tread-wise) and electrically (i.e., all connections/grounds are clean and tight, and are coated with grease or otherwise insulated as appropriate) and you carry (at least) some basic tools with you to tighten up things, in case they work loose.....
Judging from your list of added accessories (aka, "farkles"), you've made some very wise choices with regard to turning your VN750 into a pretty serious tourer. Before going on a really long trip, I would still add a couple of others:
1) A voltmeter (assuming you don't already have one). If you stator or rectifier tanks on you while on a serious trip, the voltmeter will (usually) give you plenty of advanced warning that things electrically are "going south", and you'll have a good chance to get the bike back to civilization, before you are on foot. Without a voltmeter--who knows???...
2) Seriously consider adding "Ride On" brand tire sealant to your bike's shoes (if you haven't already). The stuff just works. Unless you just really like patching holes in your tire(s) beside the road--when you could (instead) be riding. This is serious peace of mind against the vast majority of flats. Also: with this sealant, your tires will lose air more slowly, even without a puncture.
With all of that said, to answer your question...."it depends".
If you want to really "stop and smell the roses" and soak in the sights along the way, and you are in the Smoky Mountain area for instance, plan on 200 miles per day--max, since the roads in places like that are more challenging and you can't make as much time, anyway.
If you're crossing the mid-west, and there really isn't much to stop and see (like on some parts of what was "Route 66"), plan on 400-500 miles per day, for starters (then work your way up, as your endurance allows). You've wisely invested in a Mustang seat, and really (I think) the factory seat was the main inhibitor for not covering serious miles per day (I could otherwise handle it, but my butt could not).
Also: It might be a good idea to plan (at least some of) your gas stops in advance. Out west, for instance, some gas stations can be more than 200 miles apart. Poor fuel planning out there in some places can not only be inconvenient, but also--dangerous! Good idea in general, but out west, especially: buy gas when you can, not (just) when you need it!
If you have not been educated on it otherwise, read up on smart ways bikers keep from getting dehydrated (e.g., proper clothing/gear). This is a major hazard for bikers--especially in warmer weather. Know the signs of dehydration--and beat it before it beats you!
If you get tired--stop and rest! The scenery and the attractions ahead will still be there, later. Otherwise, you might not be.
The following is an AMA link that has multiple neat touring tips, that I have posted on the forum before:
and the following is a link to a previous thread about a sneaky little problem our bike has (sometimes--especially in warmer weather), and how to (easily) defeat it:
Otherwise, I wish I were going with you. Our bike really is a great machine for touring. Bigger is not always better!
Good friends, good rides, good food, good times--and good photos!
That's what really matters.
Hope some of the above actually helps.....