Washington — Firmness on the Middle East. Flexibility on arms control. Caginess about his political future. Defense of his record on environmental protection. In a brisk and wide-ranging exchange with about 50 reporters at a White House breakfast Wednesday, President Reagan responded to questions covering the record and aims of his presidency. The hour-long session, lasting nearly twice as long as the typical press conference and unhampered by the glare of television lights , gave added insight into an administration that is finding the tasks of governing much more difficult than those of campaigning.
Asked to grade his performance thus far, the President said his greatest disappointment is a national economy that is recovering only slowly, and not getting ''everything we asked for in our economic proposals.''
''But the debate today isn't whether to reduce government spending,'' he added, ''but how much to reduce it. I think we've changed the whole tone of the debate that's been taking place over the past three decades.''
Mr. Reagan said he finds it surprising that much is being made of his pledge this week to ''take all necessary measures to guarantee the security of Israel's northern borders.'' This is in line with past US policy, he said, stressing that this protection would be guaranteed only after the withdrawal of foreign forces - including Israel's - from Lebanon.
The President repeated his offer to increase the US portion of the multinational force as a means of strengthening the position of the Lebanese government while helping protect Israel from attack.
He expressed disagreement with newly appointed Israeli Defense Minister Moshe Arens, who said recently that there should be no timetable on troop withdrawals from Lebanon. ''I think to wait for a peace treaty before withdrawing forces is wrong,'' he said. ''The longer we delay this, the more we endanger the possibility of moving on into the general peace discussion.''
Asked whether there was danger that Israel may absorb the West Bank, Reagan suggested that Israel may be using new settlements to strengthen its bargaining position once serious Mideast peace talks begin.
As for his own bargaining position with the Soviet Union, the President said, ''I think the ball is a little bit in their court.''
Asked whether he foresees a summit with Soviet leader Yuri Andropov before the 1984 presidential election, Reagan pointed to his earlier offer to meet with the late Leonid Brezhnev in New York and his lifting of the US grain embargo as signs of his own moderation.
Contrasting a superpower summit with economic conferences among allies that are held regularly with no promise of dramatic result, he said: ''I think we have to have an agenda and things to talk about, because you do raise a lot of hopes and expectations.''
In his speech to the American Legion Tuesday, Mr. Reagan outlined four points he feels necessary to any US-Soviet agreement on intermediate-range nuclear missiles in Europe: equality between the two superpowers; separate consideration of French and British nuclear forces; no mere shifting of Soviet missiles already in Europe to the Far East; and strict verifiability.
Some observers read this as an indication that the administration has moved beyond strict adherence to the President's earlier ''zero option,'' and he did not dispel such analysis at his meeting with reporters yesterday.
''We will negotiate in good faith any reasonable, legitimate proposal,'' he said.
The breakfast gathering was held in the State Dining Room of the White House, said communications director David Gergen, ''in honor of the 17th anniversary of the Sperling breakfast,'' hosted regularly since February 1966, by Monitor Washington bureau chief Godfrey Sperling Jr.
Once again, the President made it clear that he is not to be pushed into what he regards as a premature announcement of his plans for running again.
Yet he provided the most specific comment on the subject to date by saying ''there is a 50 percent chance'' he will make the race in 1984.
Key political associates of the President have, in recent days, been pushing for a signal from the President that he intends to run again.
While stopping short of such a signal, he is not discouraging political activists in their preparations for the 1984 campaign.
On other subjects, Mr. Reagan made these points:
* The administration is ''getting along very well'' with the Federal Reserve Board these days. Now ''it is up to the banks'' to bring interest rates down further.
* Making the Environmental Protection Agency into an independent agency (like the Nuclear Regulatory Commission) is ''the wrong way to go,'' he said, taking power away from elected officials and giving it tobureaucrats who are less accountable.
Proposed legislation affecting such change for the EPA, he said, ''is part of the age-old battle between branches of government.''
* Asked if he favored raising the age for receipt of social security payments , the President pointed to recent increases in retirement age and the need for solutions beyond those recent commission recommendations that address the immediate problem.
''I'm convinced that things like that - extending the age - will be under consideration,'' he said. ''I think there's a great deal of logic in something of that kind.''
* In response to recent reports that the Soviet Union may be violating the provisions of the SALT II treaty in its missile testing, the President said: ''It would be very difficult to find the hard evidence to make it hold up in court, but this last one comes the closest to indicating that it is a violation. This makes it really clear that the Soviet Union has continued its buildup.''