Although it was a third rate power, Portugal did have over $2 billion of gold reserves in 1973. The constitution of 1933 made it so that by law Portugal could never have a budget deficit. Salazar was paranoid about the country being at the hand of foreign creditors and he made sure the country could finance its imports for years without additional foreign exchange if necessary. Finally, despite the war the Portuguese economy (and that of its colonies) was growing faster than at any time in its history. Between 1960 and 1973 the Portuguese economy grew at an annual rate of 6.9%.
http://analisesocial.ics.ul.pt/documentos/1223475624P7mTE0cw8Lu53HY1.pdf
The government did build agricultural settlements in the 1950s and until the 1970s, the most famous being Cela in Angola. Below are pictures.
http://www.sanzalangola.com/galeria/albuo44?&page=1
The problem with the agricultural settlements is that they cost around $10,000 per family and many of the families preferred to move to the cities rather than farm. TAP the national airline had 14 longhaul jets in 1974 (4 747s and 10 707s) and the government could have simply paid for passages to Africa. Also, the oil royalties being paid to Portugal were well over $100 million per annum in the 1960s, a figure that would quadruple by 1972. Part of the revenue could have easily paid for poorer settlers and their families.
I think the comparison with France in Algeria is an incorrect one to make since in Algeria the settlers on average only earned 80% of what they did in metropolitan France. Also, immigration of Europeans to Algeria was nil after 1920. By 1954 79% of all Europeans in Algeria were Algerian born.
In contrast, over 100,000 Portuguese were emigrating each year in the late 1960s and early 1970s. Part of my family lived in Angola and others lived in the U.S. the perception was that in Angola life was better.
Also, in Algeria most of the population is Arab, they speak a single language, share a single religion and are somewhat educated. In Angola and Mozambique you have dozens of ethnic groups who often hate each other, it's no coincidence that both countries were plunged into civil war after independence. Also, fewer than 90% of the Africans can read or write so they are essentially a much more easy population group to control.
Finally, unlike in Algeria you never saw urban violence in Angola or Mozambique. There were no bombs going off in cafes or in city streets. The settlers were unaffected by the war. Also, unlike Algeria the vast majority of the settlers were urban dwellers in Angola and Mozambique, meaning they were not interacting with landless peasants. The guerrilla movements in Angola operated in the remote sections bordering the Congo and later Zambia. In Mozambique they operated on the Tanzanian border and the border with Zambia after 1969. Hence, making the comparison to North Africa is a poor one at best.