This all sounds like a little more than simple episcleritis which is more superficial and does not cause much internal inflamation (inflammation) like uveitis. You obviously have some form of ocular inflammation whether you want to call it episcleritis, scleritis, uveitis or pan-uveitis - it all depends on the exact findings but all are similar in that they can have multiple possible causes and a properly directed medical workup is needed focused depending on your symptoms and findings and history. Now, yes, these eye findings can definitely be related to systemic inflammatory conditions like arthritis, lupus, rheuamatoid arthritis, polymyalgia, ankylosing spondylitis and more.
MJK MD