Sarge, don't be afraid to start too conservatively, worst case scenario if you do that is you can prolong the training cycle 2 or 3 weeks for even bigger net gains, not too bad actually.....if you're too generous to yourself to start, worst case scenario is you blow yourself out too soon and have a crappy experience with this......so don't feel like you can't err on the side of caution, this is a lot of volume, despite what it looks like 'on paper'.....and you're adding weight to the bar every week.
On the bench, make sure you're not flaring the elbows, and don't grip crazy wide, even competitive powerlifters train with a narrower grip when they have the shirt off, those 2 things should help the shoulder. When you start piling on size you'll love the barbell much more than the dumbells, the body doesn't know points, angles, planes, and all that stuff, all it knows is total work, and you can really overload the upper body with a barbell. Also, you can make 5lb jumps on the bar, most places have dumbells in 5lb increments, which is a 10lb jump and will bring upper body pressing to a screeching halt sooner rather than later.
Don't worry about 'only' training 3 days a week, with the volume and workload, you won't want to train anymore. I remember mm107 had that very same concern, so ask him about it, you really won't want to and won't be able to train any more, unless they are cardio/ar type workouts.
How many cals a day will you be eating? Do you have a bodyweight in mind or any strength goals? I also never asked how tall you are? You look very lean with a lot of room on your frame....this could be very fun. Good luck to you, I'll be following along.