To me, too nice is giving them something that is beyond fair considering they have left you and the M.
Unless they are attacking you the position should be 'friendly neighbour'. If they ask for a small favour and it's not far out of your way then helping isn't being too nice. If your asked to do something you feel is unfair or you are being used then doing the said action is being too nice.
If you feel like you are a doormat you probably are in someway.
If you accept being used or treated like a doormat what does that say to your WAS? Whether it's actually noticed or it's just subconscious, it's not attractive and you stay in the same position or very possibly you take a further step back.
If you say no because you respect yourself they will be angry because they are not getting their way.
A few weeks ago my W and I had an argument and I stood my ground more than I ever had before. She was furious, throwing D's, L's and custody at me like ninja throwing stars. She hated me but i think I gained her respect.
M36 W31 S4 S2 T5 M4 BD Jan12 S July12 Recon Sep12-Nov12 ILBINILWY Jan13 OM x 2 in 2013 W wants R July 13 I start D. Jan 14. Meet GF Nov 13 Have I changed enough? Jul 14