You can contact me and tell me what the piece is and I will give you support so that you can create it without problems. I may send you additional documents or videos to guide you.

Unfortunately the eva foam material is not approved by the 501st Legion, they are only allowed these types of materials or like materials: White fiberglass, ABS (Acrylonitrile Butadiene Styrene), HIPS (High Impact Polystyrene), or Polyvinyl chloride (PVC). Removing this requirement would be worthy of approval. For more detailed info in https://databank.501st.com/databank/Costuming:TK_anh_hero

Check at the end of each product item details to see all the things you will need to make it, for example foam quantity and other important things.

Yes, it comes with guidelines for adjust the pieces to your body.
Before cutting the foam you can validate the sizes and joints of all the molds on your body, and if it is possible, test them all together in your body, because after cutting molds in foam is more difficult or impossible to adjust the parts. I recommend doing this task. It is easy to adjust the parts to your body following the adjustment instructions. Remember that although the templates are for an adult, not all of our bodies are the same. It will only take a moment to temporarily attach the molds to test them on your body and you will have better completion of the armor or helmet. Here you can see how: youtu.be/-pzVJi9I1ts

I use and recommend 8mm thickness for armors and helmets, but the thicker the better, but it is more difficult to cut the foam and give shape when it’s thicker, that's why I indicate from 6mm to 10mm, but 8mm is for me the best. Remember that this measure of 8mm thickness I recommend is for armor or helmets for adults. If it's for a kid I recommend 6mm. For some small parts and clothes it is always good to have foam from 2mm to 5mm.
I recommend using a foam density between 60 and 80 to get the same result as the videos, because HD foam cannot be shaped by heat.

Some online stores:
cosplaysupplies.com (USA & Canada), redmooncosplaysolutions.com (USA & Canada), truenorthcosplay.com, (Canada), arda-wigs.com/collections/foam-products (USA), sksprops.com (USA), thecosplaypros.com (USA), tntcosplaysupply.com (USA & Canada),
poly-props.com (UK), cosplaycrafts.com (USA)
If you know more stores that you have used successfully send me the link and I will add it to the list.

The base paint that I used is a plastic paint, a flexible paint. But you can use Plastidip instead or similar, then on this plastic paint you can apply spray paints to give it shine or color, but it is important to give the plastic base so that the final paint does not crack. The base is important that you make the coats that you can, not less than 2, more coats more flexible. Sometimes you can finish it only with the base if you want or leave it unpainted with the original color of the foam.

You can use any color if you will paint it, but it is better if the foam base color is the same color as the paint. In my case I use black because I do not get good white foam for the Stormtrooper in my country, but for Darth Vader is black. I also see in many cases that the armor does not paint it and leave it to the color of the foam.

It would not be useful to tell you how much it costs to me because I am in another country and the costs of the products are very different from yours and the products are different. Besides, most of the brands that you use I do not get them here, in my case I can spend 60 USD (without templates) approximately in everything including all the materials and tools but with very low quality, but it is not the same for you. You can get in USA excellent foam density and quality, the same for the paints and tools. According to some reviews from people in the USA they say they spent on all materials 100USD or less to build and paint all armor.

The cream is a flexible plastic seal that when dried becomes a semi-soft plastic and is used to cover joints and to make the piece look more homogeneous. You can use the KWIK SEAL PLUS. You can also use a product called Foam Clay to achieve the same, which is a moldable foam.

I use a contact cement from my country to glue. I suggest use Weldwood - DAP or Barge contact cement but I have never used them, so I recommend that you try and choose the one that works best for you. The contact cement have to be liquid and dries fast.
www.dap.com/dap-products-ph/weldwood-contact-cement/
www.bargeadhesive.com/products.html
The hot glue is not recommend for all the joints, only use it to reinforce from the back.

I recommend not scaling the actual size of the templates. Print at actual size by checking the printed scale with a ruler on the first page.
It will only take a moment to temporarily join the molds to test them on your body and adjust them. You will have a better finish of the armor. Here you can see how: youtu.be/xSt6kH9D7lM
The video shows the task with an old stormtrooper template, but gives you an idea of ​​how to adjust it. See also the recommendations in pdf, it also shows how to adjust each part. If you scale the template, you will be wrong. Use the actual size and extend the mold you need to your body.
You can validate the standard sizes of the template with your body:
Adult Measurements Guide