The Baltic states I don't think they'd have good relations with us (given how we did annex and rule over them for some 50 years), I'd argue a good olive branch to make would be to outright return territories they lost to us. We'll have to rebuild relations one step at a time, and mend the fence. We should also give recognition to Soviet crimes against them, such as ethnic cleansings.
Honestly we only need them to be neutral, on their own they are pretty insignificant so letting them go is fine. Generally even as part of Nato, it's not weather Baltic States will join Nato, it's about weather Nato will receive Baltic States, that ball is in USAs court , as is our future relationship and even then it's US tax payers that will foot the bill for Baltic defense so making concessions to the Baltics makes no sense as Poland that's next door to us as well will probably join NATO so geopolitical situation even with friendly Baltics will be the same and if they join EU? Well EU has interests to keep relations friendly.
Regarding giving up territories, outright no. I'm against any territorial concessions (part of those belong to Belarus and lets not forget that they already have some territories with Russian minority which they can keep). Same as any form of concession really, basically anything unpopular at home, eventually it's in their interests to normalize ties but if they don't we have luxury to just ignore them.
I'm of opinion that we aren't in such position where we need to make concessions as we only need "normal " relationship. Like and dislike have no place in geopolitics and if we acknowledge something against them we must do so against others. To sum it up I'm in favor of ground zero relationship, Soviet Union is gone and so it payed for its crimes. Russia itself was member of USSR and had suffered just as much at the hands of Soviet government (including territorial loss) while people of Russia had no influence on decision of Soviet government.
Regarding defense Pact? New Union is planned to have unified army so it should have the same function as military pact. Of course I'm in favor of strategic autonomy for Russia where it has its own army and in exchange every other member states gets its own army. But having its own army doesn't mean that we won't defend other member states, or vice versa, instead of creating separate defense treaty I'm more in favor of adding territorial integrity clause to New Union and defense clause , basically New Union is confederation and territories of its members are its territories. That means attacking one member is attacking all members, or better said attacking New Union itself.
Just think of it as more centralized EU (which New Union was planned to be) that handles its own defense. Basically think of New Union as highly decentralized state that will defend itself if attacked.