Israel withdrew from Sinai due to immense international pressure, especially from US and the USSR. Furthermore, Israel did not originally undergo that campaign alone and were aided by both the British and the French (which both could very much do without being associated as having helped Israel secure Sinai).
When Israel invaded Sinai again in the late 60's and 70's, Egypt offered peace, recognition of Israel and the permission of Israeli ships through Suez and Israel refused to accept this. It was only after Egypt launched a major military campaign against Israel in Sinai in 1973 that Israel eventually conceded to a withdrawal and agreement.
This also ties into the Golan Heights. There is a reason why the Assad family has been left in power for decades in Syria and it is directly related to Golan Heights, for which the Assad family was very handsomely rewarded both politically and financially.
As for Gaza (which the 'disengagement plan' was a Sharon devised policy), perhaps we might take heed to the words of top Sharon aide Dov Weisglass on the matter where he stated that the policy would prevent the possibility of a Palestinian state for years to come. Israel also maintains control over Gaza's airspace, borders, power, infrastructure and import/export...but in the 'name of peace' of course.
Israel does not maintain control over Gaza's borders. Egypt is in full control of Gaza's border with Egypt. The restriction on Gaza came only after Hamas was elected into power.
As for Egypt, everything you've written is a total fabrication. The Egyptian attack in 1973 was easily repelled by the Israelis. The Israelis then began to cross the Suez as part of their counter-attack. Israel had the entire Egyptian third army trapped until the USA put massive diplomatic pressure on the Israelis to withdraw.. The piece agreement had absolutely nothing to do with:
Egypt launched a major military campaign against Israel in Sinai in 1973 that Israel eventually conceded to a withdrawal and agreement.
Furthermore, the Sinai wasn't returned until several years later. Israel didn't reject the "Sadat Initiative". It was part of the process that led to the eventual negotiations that led to the peace treaty. In fact, Israel supported the initiatiave, and most speculate it was Jimmy Carter who slowed things down in order to secure the USA's position with Egypt in the cold war. Sadat had been invited by the Israelis to speak before the Knesset. Even then things weren't really slowed down at all. Sadat spoke in December of 1977 and gave his proposal for peace. By 1978 the Camp David Accords were signed, and by March of 1979 a full peace treaty had been reached.
The Egyptian leader who signed the deal was assassinated by his own people. The peace deal which had come out of the Camp David Accords, not pressure by Egypt to "concede". THe only thing Israel got in return from giving up huge amounts of land was a peace treaty. Egypt got billions of dollars a year.