The distinction crucial for resolving the Apology difficulty, I think, is that between 'someone' and 'what belongs to someone':
I tried to persuade each of you not to place care for what merely belongs to himself over care for himself--viz. that he be the best and wisest he can be--nor to place care for what merely belongs to the city, over care for the city itself; and to show care for others in just the same way (36c).
Thus the good or bad of 'someone' is the good or bad condition of his soul, which would consist in his having, or lacking, the virtues; the good or bad of 'what belongs to someone' would be the better or worse state of those things that are commonly accounted good or bad.
e0pixeirw~n e3kaston u(mw~n pei/qein mh_ pro&teron mh&te tw~n (5) e9autou~ mhdeno_j e0pimelei=sqai pri\n e9autou~ e0pimelhqei/h o3pwj w(j be/ltistoj kai\ fronimw&tatoj e1soito, mh&te tw~n th~j po&lewj, pri\n au)th~j th~j po&lewj, tw~n te a1llwn ou3tw kata_ to_n (d.) au)to_n tro&pon e0pimelei=sqaiSocrates intends this, I think, as a distinction between the soul (which is what he thinks each person is), and everything that pertains to someone besides his soul. This is especially clear from the way that distinction is wielded in Alcibiades I, 128a-133e. Some exemplary passages from that dialogue:
Well then, what does it mean to care for (epimeleisthai) ourselves? --I'm afraid we often think we're caring for ourselves when we're not. When does a man do that? Is he caring for himself when he cares for what belongs to him? (128a)
Since a man is neither his body, nor his body and soul together, what remains, I think, is either that he's nothing, or else, if he is something, he's nothing other than his soul. (130c)
We were afraid that we might make a mistake about caring for ourselves and unwittingly care for something other than ourselves. ...And the next step is that we have to care for our soul and look to that... and let others take care of our bodies and our property. (132c)
Senn is right to notice that Socrates draws an implicit distinction between 'harming' (blaptein) and 'bringing about bad' for someone. The former would involve actions, and especially speech, which are designed to encourage people to be bad: a harm is something that makes 'someone' worse. The latter would involve taking away or preventing good things, or producing or hindering the removal of bad things, as regards 'what belongs to someone': doing bad is doing something that makes 'what belongs to someone' worse (than would have been the case otherwise). (What is important for Socrates is in the first instance what is made worse off, not how this happens; hence Senn's distinction between 'damaging' and 'obstructing' is not to the point.)
Thus the resolutions:
"You would not injure me (blapsete) so much as yourselves" (30c). That is: 'You can make me worse only in what belongs to me, and in doing so you make yourself worse in what you are.'
"It's not permitted that a worse man should injure (blaptesthai) a better" (30d). Suppose someone aiming to be good (a better man) and someone who does not care about being good (a worse): the latter cannot, just by what he does or says, make it so that the former does not care about being good, or make it so that the former is less good.
"Bad people are constantly working something bad in those around them...", and thus bad people are "harmed (blaptesthai) by those they associate with" (25d). Socrates here compares groups of companions who are bad (who encourage corruption in one another), with groups of companions who are good. He actually never talks about the case (fantastical, surely, for him) where a good person is surrounded by bad companions.
"Since I am convinced that I never wronged any one, I am certainly not going to wrong myself (adikein), and say of myself that I deserve anything bad, and propose a penalty of that sort of myself" (37b). Here I think adikein=blaptein. This is a moral injury Socrates will refrain from because he aims to be good.
"Shall I choose instead a penalty which I know to be an evil?" (37), viz. in what belongs to me--it being assumed by him that, all other things being equal, if he were to choose a greater over a lesser evil in what belongs to him, then this would be moral badness, which he must avoid above any badness in what belongs to him.