Hi, @BudeanuJr ! Yes, this is possible. The method I described is how each of your products can have their own additional information. The reason the information you enter is appearing on all products is because you are entering it into your Default product template using your theme editor, instead of using the product settings in your Shopify admin.
The steps I shared previously will help you add additional information to each of your products. If you’d like to update your products in one go, rather than one at a time, I recommend using the product bulk editor. This will allow you to update the information for each product you select, all on one page (so you don’t have to click into each product separately). You can read more about using the bulk editor here.
You should be able to have more than 100 words in a product description. I tested it out on my end and I didn’t notice any problems. I can look into it further if you’re noticing an issue when you try to enter more than 100 words.
Please let me know if you have more questions! In the meantime, I also wanted to share this guide to help you create your product pages. It has helpful information on ways to highlight your products, and make your product pages more appealing to customers.