Vehayah" is a Lashon of Simchah. How is this applicable here?
Oznayim la'Torah: It is a Simchah when the master treats his Eved Ivri with such respect that the Eved loves him and his family to the point that he does not want to go free 1
See Oznayim la'Torah.
What are the implications of "Ki Aheivcha" and of "ve'es Beisecha"?
Kidushin, 22a: It implies that if the Eved Ivri does not love his master 1 - even if his master loves him - or if his master does not have a wife and children, 2 his ear is not pierced and he is obligated to leave immediately.
Targum Yonasan: See answer #1 - only he translates "Beisecha" as 'the members of his master's household'.
What are the implications of "Ki Tov lo"?
Kidushin, 22a: It implies that if the Eved Ivri is sick, 1 his ear is not pierced and he is obligated to leave immediately.
Lame or blind. See Torah Temimah, note 57.
The Gemara in Kidushin, 22a extrapolates from here that if the master does not have a wife and children, the Eved Ivri cannot become a Nirtza. But our Pasuk does not mention children?
Moshav Zekenim: Perhaps they are included in "Beisecha". 1
Tosfos ha'Rosh and Maharit #1 (both in Kidushin 22a): Indeed, the master need not have children, only a wife, who is called "Beiso" regarding a Kohen Gadol. The Gemara states that the Eved Ivri must have a wife and children, and so must the master - though this is not precise.
Maharit #2 (Kidushin 22a): Granted, if the master has children, 'loving the master's wife' means finding favor in her eyes through endearing her children. However, if he has no children, it is inappropriate to say that he loves his master's wife!
Atzmos Yosef (Kidushin 22a): Perhaps they are included from the word "ve'Es Beisecha" - since 'Bayis' S'tam refers only to a wife.
The Gemara does not mean that his master must have children, but that the Eved Ivri loves the household 2 - whether it consists of a wife alone or a wife and children.
The Kohen Gadol too must have a wife on Yom Kipur, since the Torah writes in Acharei-Mos Vayikra, 16:6 "u'Ve'ad Beiso" (Yoma 2a), but we do not find that he must have children?
Why does the Torah add the (otherwise superfluous) word "Ki Tov lo Imach"?
Moshav Zekenim (Sh'mos 21:4): To teach us that if the Eved Ivri is lame or blind (and his master is not) he cannot become a Nirtza. 1
Kidushin 22a #1: To teach us "Imach" - 'regarding food'; "Imach" - 'regarding drink'; "Imach" - 'that you should not eat white bread, and he, black bread'; "Imach" - 'that you should not drink vintage wine and he, wine straight from the vat'; "Imach" - 'that you should not sleep on soft covers, and he, on straw'. From here they said that someone who purchases an Eved Ivri, purchases a master for himself! 2 3.. Kidushin 22a #2: To teach us that if his master does not love him - even if he loves his master - the Eved Ivri cannot become a Nirtza.
Kidushin 22a #3: To teach us that if his master is sick and he is healthy - the Eved Ivri cannot become a Nirtza.
Kesuvos, 63a: To teach us that the master cannot say to the Eved Ivri 'Work for me and I will not sustain you!' 3
It is unclear what the Din will be if also his master is lame or blind. Presumably, it is like the Gemara's question about if both of them are sick - which is left unanswered.
Tosfos in Kidushin 20a (citing the Yerushalmi): If the master has only one cushion, he must allow the Eved Ivri to use it. The Ritva in Kidushin (Ibid.) maintains that the master may live better than the Eved Ivri, only he must treat the Eved Ivri with respect, like other workers - as opposed to the Rosh in Kidushin 1:27, who holds that "Tov Lo Imach" is confined to an Eved Ivri, and does not extend to other workers.
See Torah Temimah, note 61.