Sometimes when people try to run a stove with the main thought being save pellets they shoot themselves in the foot instead. Those huge swings in house temp eats through pellets. If he kept it more constant he would be more comfortable and use no more than now and maybe less.
As to blower, a low blower will keep the room warm that the stove is in, it also will cause early room temp shut down never allowing for heat to get out into the rest of the house. The result is a cold feeling house and one warmish room. A high blower will push the heat out into the house more, that's why it has a blower. He needs to sacrifice a few pellets to get to know the stove, turn the dial up to about 72 ish and the blower on high. I know this only because I've been through it !! Once the house is caught up and the stove starts cycling turn the blower to medium and leave the temp alone. Let the stove cycle to maintain even temps in the house. All that up down, on off stuff accomplishes nothing but discomfort with lot's of high burning rates and tall flames in the stove.. When a P series Harman plays catch up it can clean the hopper out fast ! From there he can decide what mode he ultimately wants to run the stove in. But he could be cruising along with a warm house and the stove sipping on a steady diet of pellets instead guzzling them to catch up all the time. . I understand it's hard to program ones head to think steady, constant heat uses less fuel.
A lot of us Harman people tape the room temp probe to the back of the hopper. The probe itself, the very end should be out in the air, not touching a surface and should be well up off the floor. I have mine level with the top of the hopper back and sticking out maybe 3 inches away from the hoppers metal surface. That's a good starting point anyway.
FWIW, I heat 1800 sq ft with a P61, I put the temp on about 73 and leave it there all winter long. If the weather outside starts dropping down to 0 I might bump it up a bit and or turn the fan up from medium to high. The only time I run low fan is if we have company visiting in the living room and I may well put the stove in stove temp mode then too.. If the weather warms I might lower the temp to 70 at night. But average day in and day out in the winter, the stove is set to 73 and the main house is 73. I can't stand being cold sitting in my own house. The only variable really is pellet use as the weather changes. On those cold 0 days, ya I'm going to burn nearly 3 bags of pellets, it's cold out and the demand on heat is high. On warm days a bit over one bag. On average two bags a day overall, so I just plan my pellet use on two bags a day. My house is rather loose with so so insulation. He has the right stove for his sq ft, he just needs to learn to use it and ya it's going to burn some pellets, probably less of them than I do..
thread at the top of the forum about what your manual doesn't tell you might prove helpful too. Harman website has lots of Owner resources - operating and maintaining instructions and videos. 
