Arlin, you can't use a larger fan on your 1 HP motor, at least not one much larger. The more air you move the more amps (power) the motor draws. If you use too large a fan you will burn out the motor.
If you can't afford a larger DC, you should work to maximize the airflow through your current system (while staying within the amp. limits of your motor) and minimize the amount of air it needs to pull to do a good job. That means use filters that minimize the pressure drop. You can do that by using a much larger bag on it than the OE one.
American Fabric Filter Co. can make you a custom sized bag that will give you maximum flow (cfm) while still collecting whatever size particle you want, 2 micron for example. OK, that's the best you can do on the flow side of things. On the other side, you want to minimize how much air you need to move. That means using as large a pipe and/or hose as possible while still moving the dust at about 3500 fpm (I think), and eliminating all the leaks in your piping, hoses, fittings, etc. For a 500 CFM DC that means your main pipe should be 5" in diameter. It also means using fittings that pull the chips and dust from as close as where they are produced as possible. You planer and jointer should have dust chutes available from Grizzly. If they have any leaks you should seal them up. If they are completely inadequate you would have to build something better or find someone who's already done so and copy what they did. Same thing for your cabinet saw and bandsaw. There are lots of poor DC concepts when it comes to both those pieces of equipment, but there are few good ones, too. The best advise I can give you is to collect the chips and dust as close as possible to where they are generated because it minimizes how much air is required to do it. A 4" hose in the back of a cabinet is about as poor as it gets, yet that's what you see on many old design saws. Look at the new saws how they use a shroud around the blade to capture the chips and dust and you'll see what I'm talking about. Same thing with bandsaws. A port in the back of the lower wheel housing is not going to be very efficient, although they do work if you have enough CFM which you don't. Dust collection fittings that fit right up under the lower wheel guides are what I'm talking about.
For your lathe you need to buy or build some kind of hood that is as small as possible and sits as close as possible to the work. This maximizes the velocity of the air and minimizes the amount of air that needs to be handled. A piece of 6" PVC pipe cut in half fit up almost around your stock, with one end blocked off and the other connected to your DC hose might be something along the right idea.
Your problems won't go away by installing a cyclone, although that will reduce the time interval for cleaning the bag. Spend you time and money on the things above first.
John
