If the hose (garden hose) is reasonable quality and in fair shape, 40 psi isn't too likely to hurt it, so you could put the pump at the tank and pump the 40 psi into the hose.
At WVA we commonly use a couple of hundred feet of ordinary garden hose, with an RV "regulator" (50 psi limiter) at the inlet to the hose, and have little problem. They've been known to crank the pressure up to 75 or 80 psi at the faucet so that the 15 or 20 hoses hooked up to it can all get something out of the other end, and the garden hose with the "limiter" at the outlet end will sometimes swell up and bust with 70 psi going into it; but 50 psi going in doesn't usually hurt a reasonably good hose.
If you have to run power for 100 feet or more, I'd suggest you try to use AWG12 or better wire - not for carrying the power but to minimize the voltage drop. Even at the couple of amps that a 3 gpm 40 psi pump will draw, 100 feet of lighter duty wire may mean the pump is running at 80 or 90 VAC instead of 110, which may be hard on the pump motor.
If it's more convenient to put the pump at the hose outlet, I wouldn't expect the pump to be able to "suck" hard enough to collapse the hose. The pump will only run when there's output flow, and will shut off when the flow stops and the pressure comes back up, so it's a matter of whether the hose can deliver enough flow to keep the pressure up that determines how hard and how long the pump will "suck" on it. The pump can't "suck" the pressure by more than 15 psi, so when it turns on you'll have up to 15 psi plus your 3 psi from the tank height feeding water in at the tank end, so very roughly 6 times the inlet flow to the pump, compared to what dribbles out of the open hose end.
A #8 or #10 rubber "fender washer" (0.112 or 0.125 inch hole in it, and try for a 3/4 or 7/8 O.D. or trim the O.D. to fit) stuffed into the connection where the pump outlet connects to the PVC will limit the outlet flow about like the "flow restrictors" used in some shower heads, and will allow the pump to "see" enough higher pressure to shut off a little quicker, if it's sucking more water volume than the hose can deliver with the pump outlet wide open. (A hole of about 0.1 inch diameter will restrict flow to about 1.5 gpm with normal 35 psi pressure to a shower head.) A restriction at the pump outlet may make the pump cycle on/off more frequently, but that's pretty much normal for small water pumps.