Water in the air will hold the heat more, that's why air conditioning takes water out of the air. Unless you cool the air in the room, you will always be only able to cool the tent to a few degrees below ambient air temps.
8 inch fan will be way too strong, even with a controller on its lowest setting and forcing air in the tent.
I think without air-conditioning, or a smaller light, you will be really struggling, to keep a useable environment. Your other option is a sealed room with extra CO2, but if your money is tight, that's out as well.
I made the same mistake bought a 1000w light then couldn't use it without cooking the plants, even in my 8x8ft flower room I need air-conditioning in the summer to keep it below 80f.
For a 4x4 tent a 400w hid and HPS is adequate, 600w is the upper limit.
Your next problem will be plant height, with a 1000w light you will need at least 20 inches underneath the light, to the top of the canopy, or the plants will get damaged from light intensity. You will probably have at least 8 inches above the light so that's 28 inches of growth height you have lost. Pots will lift the plants about a foot, so now you have about 36 inches on the average tent height, for your plants to grow up in. When they hit the stretch, you may have to bend a lot of tops over or do some LST before flipping them.
How tall is the tent?