Especially with Sindarin, I prefer receiving translation requests rather than feedback requests, since otherwise things tend to get out of hand (case in point). But Quenya is safer in that regard. Evidently so, considering that your first translation has almost no issues (other than "tenn' oio" which I would suggest replacing with tennoio). The second translation could use feedback however.
That satto is an "Adûnaic" word, not Quenya, which should be atta. And dual suffix would likely be preferable here, thus simply cormat (without atta). Continuing, there are two attestations of the first person dual inclusive suffix as "-nqu(V)" and "-ngw(V)", so using -nqua for "our (yours and mine)" is not wrong, but most Quenya experts seem to gravitate towards "-ngw(V)" forms instead, melmengwa may be preferable. Speaking of inclusive pronouns, you should consider whether it should be inclusive.
Do you imagine the phrase to be spoken by you to your spouse (and vice versa), or is it to be spoken by you two to everyone else? If the latter, the phrase should use exclusive pronouns instead, which it already does in a way, with that me at the end. The nominative/accusative form of the first person inclusive pronoun was ve (older we) but this fell out of use and more or less replaced by me (partly due to its coinciding with ve "as, like, similar"). So using me in the same line as -ngwa is not wrong, but it's not quite the only option. Also it should be met, and this dual differentiation could be enough to "resurrect" ve in the form vet (since other varieties of ve seems to be used still, only ve itself is rather archaic).
Finally, "oiossë" uses a locative suffix on an adverb, it needs fixing. I would have said "... and eternally bind us", but I'm guessing that that "in" is required for the One-ring similarity. In which case you can use oiressë instead. Now for the Tengwar transcriptions (which should not be called translations). That particular font in Tecendil does not place the tehtar correctly. Perhaps you would like the "Annatar Italic" font, made to be similar to the Ring Inscription (though there is a slight problem with it as well, the "co[rmat]" part so I fixed it manually). I will offer them in image form, here:
meluvan tye tennoio
cormat tanien melmengwa ar oiressë nutien vet