What you are experiencing is in the design of that particular machine.
My old Grizzly G1067Z also had that annoying feature of the handle being in the way of working when at it's highest setting. Methinks the design unjuneer who drew it up never worked at a lathe. Deal with it or get a new lathe.
In the price range of your lathe, like my old Griz, yes, the low speed is much too fast for big bowls, especially out of balance blanks.
Other than replacing the lathe with something more expensive, there really isn't a solution.
As much as I liked my old Griz, especially the purchase price, when I sold my antique tractor I used the proceeds to upgrade.
It all depends on what you want to do.
For the money, and in it's class, your Jet is a great lathe.
"Folks is funny critters."
Think for yourselves and let others enjoy the privilege to do so, too. ~Voltaire