Hi.
i) I must say I'm not sure about the mech here. Will think about it.
ii) Ethers are electron releasing group, so you wouldn't really expect to stabilize the charge on that oxygen. However, you've got three nitro- groups in ortho- and para- positions which set up the ring perfectly for nucleophilic aromatic substitution via the addition-elimination.
You must bare in mind that the meta-directing and deactivating effect of electron withdrawing groups (ester,ketone,nitro etc.) occurs whilst considering electrophilic aromatic substitution (i.e. Friedel-Crafts), whereas in nucleophillic AS electron withdrawing groups in o- and p- positions help it.
Normally, you would have a halogen as the leaving group and O, C, N nucleophiles. Since OMe and OEt are similar I imagine, you'd need your methoxide in excess.
Hope it helps.