First the “Disclaimer”!!!! I am no pro at this, Like you im new to the Ham Nation.
THat said, i run a similar setup with an FT-817 connected to an MFJ-1622 apartment antenna through an LDJ tuner. This too has a coil to offset the short radial, and uses a counterpoise. Your calculations are right at 33’for 40 meters. Im using a single wire streched out in my apartment on the floor. I average about a 1.5/1 SWR with this configuration. I also have heard that more radials will help but have not experimented yet. So far my punny 5 watts has gotten my out to Michcan, Erie Pa. and the Carolinas. My problem is getting stepped on by the 100 watters????.
Ill be curious to hear what you come up with as I will be doing SOTA expeditions this summer and am thinking of more radials.