Guru Vimshottari Mahadasha modern view - Barbara Pijan Lama Jyotisha

48-50. if Shukra is Dhana's, or Yuvati's Lord , Loss of wealth, fear of premature death, Antagonism with wife etc. will be experienced,

These shlokas refer to house lordship, not house occupation.
Naturally, if Shukra is the maraka L-2 or L-7, Shukra's periods will contain awareness of death.
Shukra becomes a killer for Mesha, Kanya, and Vrischika lagna. Shukra = a double-killerfor Mesha lagna.
Shukra is a pleasure-lover, so when Shukra becomes aware of the presence of death, He does not welcome this threat of losing the flesh-body's access to sensual pleasures.

Thus Shukra feels fear or frustration about death.

Shukra is not a wise graha. He is very materialistic and He likes it that way. (Shukra is Shani's BFF.) He does not accept death very gracefully despite His overall graciousness! Death logically gives a loss of material wealth. The basic reality of death is that "you can't take it with you".
Also., if Shukra = L-7, seventh = 6th [poverty]-from-2nd, which means that certain set-ups for L-7 Shukra can stimulate "poverty of money" I.e. 6th-from-2nd.
One of the major causes of the native 's experience of poverty of money is the agent who spends most of one's money and that is the business partner, attorney, consultant, adviser, or wife - the agents of Yuvati.

Antagonism with wife comes from Shukra's capacity as lord of dhana bhava. bhava-2 is inevitably the 6/8-from-7th.

bhava-2 rules second marriage and if the culture permits more than one wife (which most cultures traditional ly did) then the first wife rather naturally resents the second wife.
Yet if a man starts to gain some wealth due to Shukra one of his first acquisitions is typically an additional wife.

bhava-2 also rules the mouth.

When Shukra is empowered in relation to bhava-2, the mouth is looking for sweet pleasures, especially ladies and wines. First wife is likely to take a dim view of these delights, thus antagonism with wife.

Here is where you can see the effect of the Sanskrit shloka "telegraphic" style creating a choppy English output.

The initial explanatory causative phrases "because Shukra becomes the lord of the 6/8-from-yuvati ruling marriage partner" or "because yuvati is also 6/8-from-2nd ruling hoards of wealth" are not articulated.
These missing parts occur mainly because most of the people who received these shloka for passing down through memorized chants did indeed already know the vidya pretty well, so it wasn't much trouble for them to fill in the connections.
However, it's undeniably hard on us modern beginners to get the transmission in bits and pieces.
We have to fill in the missing pieces with logic.

Similarly, Parashara says -- 45-47 1/2. if Shukra is in a Kendra, Trikona, Or in the 2nd from the Lord of the Dasha.

There will begain of wealth;happiness from wife; meeting with the king, increase in the number of children, conveyances and cattle, enjoyment of music, society with men of learning, Availability of sweetish; preparations; giving help and assistance to kinsmen etc.,

This shloka is about graha in occupation of a bhava, not lordship.

A material-sensual benefic in kendra (corners) or trikona gives materially pleasurable results.
Shukra = karaka for sweet tastes (sugar, alcohol) pleasures of the five senses, valuable things, beauty, money, art, music, and harmonious relationships.
Naturally all of these pleasures will arrive if the sukha-graha is well placed.
Again some of the lead-in phrases are not fully articulated.

If Shukra occupies domains 1, 5 or 9 pleasures of children are enhanced.

In house-10, prestigious meetings with the king and the enhanced public reputation it brings. In house-9, men of learning (universities, temples).
The 2nd-from reveals matters of the family lineage.
During periods of a well-disposed Shukra that is 2nd-from the mahadasha pati, one may find one's resources (house-2, 2nd-from) have increased to the point where onecan enjoy the pleasure of giving help and assistance to those in one's family lineage, the kinsmen.

And so on, with Shukra giving the pleasures derived from accumulation of resources (wealth) and fleshly sensual experience, according to the house in which Shukra lives.

I hope it is clear that there is no contradiction whatsoever in the BPHS [ Chapter 56: Effects of the Antaraa Dashas in the Dasha of Guru] shloka 45-50 re: Shukra. There are however persistent literary translation issues, and for these let us have compassion for both the translator and the reader!

45-47 refer to house position,
whereas 48-50 refer to house lordship.
One may have simultaneously many pleasurable accumulations of wealth and prospects for sensual experience (esp through marriage/women) and be at the same time afraid to lose these things, or be in conflict with someone who doesn't want one to have these things.

Wishing you best success in Jyotisha studies,

Sincerely, Barbara Pijan Lama, Jyotisha