Learn English – the use of the word “Bastard”

Outside of neutral meaning as "out of wedlock child", it can have a slightly positive meaning in context of "very impressive". It is always slightly derogatory but sometimes it carries a load of awe. Like, when the opponent in sports pulls out a truly impressive stunt gaining a lead against the odds, you might hear "that bastard" uttered with humor and respect.

One frequent phrase is "Magnificent bastard", a person who picks morally ambiguous, or outright immoral means to achieve their goals, but are exceptionally efficient and impressive at that, and not ashamed of it in the least, arising more awe than hate, often arrogant but still likable. Most impressive and likable supervillains (and quite a few morally ambiguous heroes) from fiction are often characterized that way.

There's also a strictly humorous positive use for this when a person uses subversive means to force someone for something good against their will. Say, you try to lose weight, but your willpower often wavers. If your partner steals all your sweets, you might say "you bastard", while essentially praising them for aiding you.

Merriam-Webster's Eleventh Collegiate Dictionary (2003) offers this entry (which includes a usage note) for presently:

presently adv (14c) 1 a archaic : at once b : without undue delay : BEFORE LONG 2 : at the present time : NOW

usage Both senses 1b and 2 are flourishing in current English, but many commentators have objected to sense 2. Since this sense has been in continuous use since since the 15th century, it is not clear why it is objectionable. Perhaps a note in the Oxford English Dictionary (1909) that the sense has been obsolete since the 17th century in literary English is to blame, but the note goes on to observe that the sense is in regular use in most English dialects. The last citation in that dictionary is from a 1901 Leeds newspaper, written in Standard English. Sense 2 is most common in contexts relating to business and politics {the fastest-rising welfare cost is Medicaid, presently paid by the states and cities —William Safire}

Interestingly, in all three examples that the OP cites, Pynchon seems to be using presently in the (relatively) uncontroversial sense 1b of the word: "without undue delay : BEFORE LONG." Replacing presently with before long in each case, we get these results:

1. Tracking from one group of attendees to another, locating before long a normal-enough-looking citizen with an interest in migratory-bird hunting and conservation stamps, known to collectors as duck stamps, and his perhaps-less-involved wife, Gladys....

2. He and Maxine join a small group who have begun drinking the stuff and passing jars around, before long finding themselves a few miles out of town at El Sueño Tropical, a half-built and for the moment abandoned luxury hotel, screaming through the corridors, swinging across the courtyard on jungle vines, which have found a purchase overhead, chasing lizards and flamingos not to mention one another, and misbehaving on the moldering king-size beds.

3. On that caper it was the Practical Elf who acted as agent and before long bagperson, holding up the Strubels for a sum nicely in excess of what they had initially offered to buy Heidi, the little Polish snip, off.

In none of these three examples does the wording strike me as wacky, objectionable, or in any way incoherent. Each simply uses the older (but still current) sense "before long" of presently instead of the newer (but still old) sense "now" of presently.