These rules require the subjunctive tense in order to express contemporaneity, posteriority and anteriority in relation with the principal clause.
2.
The principal clause is " pennies saved two at a time ", hence the main verb is " saved ".
3.
*As far as my knowledge of English goes, the subordiante clause will follow the tense of the principal clause.
4.
Many items are still found in English textbooks which were felt by Rivlin to have no functional value, e . g . noun as substantive, abstract noun, person and case of noun, participial phrases, principal clause.
5.
In principle'might'in " I thought I might not do it " could be both but I find that'might'is relatively rarely used as a past tense ( especially in an independent or principal clause ) but it occasionally happens : e . g.
6.
If this is from Menander ( you didn't answer; see 5th line of this page ) then it seems I am more or less right ( see 4th line of the English translation : " I well remember "; ????? of course means clearly ) although my recollections of Greek syntax are too faint to remember what use of the subjunctive this would be in a principal clause.