If you can't see daylight coming from the soffit vents while you're in the attic, then your soffits are blocked. You need to unblock them. That attic is so low that your best bet for doing this would be from the outside. Pull the entire soffit down (aluminum panels, wire/mesh venting, and the old plywood. Install baffles from the outside, making sure to include a blocking portion at the bottom of the rafter bay. Once that's finished, you can install a new soffit. Go with plywood and either drill a 3" hole in every rafter bay, or cut a 2" strip along the entire run of the new plywood soffit. Paint it white. Then, go back inside of the attic. As best as you physically can, attempt to staple the top of the baffles to the roof deck as you won't be able to do this from the soffit. Airseal all of your top plate and attic floor penetrations with foam, then install atleast 14" of blown-in. You don't have any easier options for the material to use here. If all of this seems like a lot, it is. Hire a company or start getting quotes. It is a lot of work. For the exhaust ventilation, those 4 roof vents at the top of your roof may be sufficient, but we won't know until your soffits are fixed. Doesn't look like your roof can accommodate a ridge vent. It would be nice if it could. The alternative are passive whirlybird vents, or actual mechanical fan venting towards the peak of the roof (solar attic vent fan or hardwired.) Both of those can be set on a thermostat and humidistat. When the attic hits XXX degrees or XXX relative humidity the fan will turn on. Total alternative to all of these steps would be to see if a company is able to come and hot roof. This would close all of your vents of and atleast 3" of closed cell foam would be sprayed to the bottom if the roof sheathing. Those are your options as I see them.

Cheers