It will get better. I loved my Bandit on the highway but was unhappy in the city at first. That came in time.
Hit a school parking lot or something on a Sunday. Snag some cheap traffic cones from Dollarama and do some of the low speed drills you did when you did your riding course.
I do think you made a great choice for your next bike; they are popular for a reason. A few more tweaks in the ergonomics and some more time in the saddle and I suspect you will warm up to it.
Edit: For the stalling just do the old school friction zone thing for a bit. See how much play you have before the clutch engages. Adjusting your lever might help but you are so used to when your old bike's clutch engaged. Also, being a 250 you probably were using 2000 rpm or so to launch the thing. Do that on a V Twin like your 650 which are torquey but nature and it is going to want to jump out of the hole. Just try to idle out and see what happens. Likely you just need to add a few hundred rpm to launch smoothly. On an incline yes a bit more rpm would be needed but likely not as much as you think it needs.
Weird doing a demo day. The CB 500 barely needed any throttle to launch smoothly. F6B with the 1800cc flat six needed no throttle at all, and oddly enough the 1000cc parallel twin in the Africa Twin needed a few extra hundred rpm or else it would stall! Who would have thought that a 1000cc parallel twin needed to be at a higher rpm than a 500cc parallel twin to get going? Probably something with the way that bike was geared.
You are going to learn a ton going up to a larger bike. You must notice how much better it handles and brakes as well. Some decent hardware on that bike. The components will be at a higher level than your old bike. You are likely a little jumpy with the brakes as well. That will smooth out. You will be a much better rider by the end of this season. Enjoy the journey!