I use the chia seeds the following way…
2 tablespoonfuls per pound of meat. It seems to scale pretty good that way. I have made 1 pound, 2 pound, and 5 pound meatloafs, and 2 tblsp per pound worked really well. I would suggest that as a starting place.
First I mix all my dry ingredients together, salt, pepper spices, and dry chia seeds. In my case I’m not grinding them. I have heard it done, haven’t attempted that yet.
Anyway, once I have all my dry ingredients mixed together I pour in hot water from the kettle. I don’t measure, I just pour it in and stir the dry mix until it’s a paste, not runny, although it will thicken up pretty quickly, so that might not really matter too much.
I put the meat in a gallon size zip lock bag, put in an egg, zip it shut and massage the egg into the meat. Then add in the paste, zip up the bag leaving a tiny bit to release air, try to get out as much air as possible, zip it up tight. Massage the mix thouroghly (sp? My iPhone won’t let me spell it correct and I gave up).
I split the mix in two parts now. I use a 6 inch baking dish, put the first half in spread flat. Put my special layer in next, usually 4 to 8 oz of cream cheese. Sometimes Gouda, sometimes cheddar, once I went for broke and used every cheese I had. Then later the other half of the meat mix on top. Then cover it with bacon. I like to take the bacon and cut it into squares, and cover the entire top. I use scissors (I learned that in Korea, have a pair of cooking scissors. They come in real handy!) since it’s so small I bake it in my toaster oven with convection on, helps to crisp the bacon. 350 for 30 minutes. On occasion I need to get the bacon to crisp a bit more so I just put it in broil and watch it crisp up.
This is a version of @carl philly bacon wrap meatloaf. I just pledgerized where I had to because I could never get the damn stuff to roll up like he did. Mine always turned into a meat wad, instead of a roll. So i settled for layers 
You might have to play around with the moisture level. I’m not a good cook. I just try to remember what works and repeat that next time. As far as the amount of water in the chia seeds, they are going to soak up a lot. In cold water, they take about 20 minutes (I think) to reach saturation , with very hot water it takes just a few minutes. So, you might need to play it by ear. If the meatloaf comes out too soggy, use less water next time. Just remember to keep track of how much you used
. Mine came out really spongy this last time. But I added in an equal amount of flax seed with the chia seed. I’ll forgo the flax seed from now on. I just added it because I could. Not always the best reason to do something.