Welcome to the wonderful world of charcuterie!! The stiffness is relative. I made the same observation the first time I did capicola. Allow it to lose 30% of its weight and cut it open. If it looks and smells fine, give it a try. I’m not sure what the consensus is, but I’ve cured everything I’ve done for a minimum of two weeks. There’s a formula for weight/thickness/curing time that I can’t recall right now but a google search should reveal the answer.
I studied liberal arts for 7+ years after primary school and know little to nothing about science, so take my advice with a grain of salt.
Sorry I can’t help you with your sealer issue. As long as there is no liquid being pulled out, you should be able to get a good seal. I’ve had horrible luck over the years with foodsaver sealers. I’ve had two automatic sealers from costco that broke with only minimal use. I’m thankful for their generous return policy. Since I’ve been doing charcuterie, I’ve been using the “game saver” version with decent results, but it too occasionally makes funny sounds and doesn’t work properly when I’ve used it less than 40-50 times in the past 4 months. I don’t expect it to last long. Overall, I’ve been completely unimpressed with anything put out by foodsaver. Others may disagree.
Good luck! I’ve stressed over these issues, too. I liken it to homebrewing. The author of the beginner’s book everyone reads stresses the importance of following directions, but at the same time, his advice is, “relax and have a homebrew.” I think the advice translates to our endeavors, except with funky beer, it just tastes funny. With charcuterie, there’s a risk of more severe pathogens. However, I “think” there’s way less worry with whole muscles. The danger is having nasty stuff grow on the outside (my understanding.) Just like a steak, if you make sure to inhibit or eliminate the growth of unfriendly bacteria on the outside of the meat (through searing or curing), you should be fine.
Sodium nitrate and nitrite are extraordinarily powerful curing agents. I forget how much #1 and #2 I have on hand, but I calculated that if distributed and ingested, there’s enough to kill about 40 grown men in its pure form. Nasty bacteria don’t stand a chance.