It is not a condition of fasting being valid that one should pray in congregation

It is not one of the conditions of fasting being valid that
one should always pray in congregation in the mosque, even according to
those fuqaha’ who say that it is obligatory to pray in congregation. Not one
of them ever said that fasting is not valid unless one does that, or that
the reward of fasting will be lost if a person prays by himself. The justice
and generosity of Allah, may He be glorified and exalted, are too great to
allow a great good deed and act of worship such as fasting to be lost
because of a shortcoming in another act of worship, namely prayer in
congregation. Allah, may He be glorified and exalted, says (interpretation
of the meaning):

“Surely!
Allah wrongs not even of the weight of an atom (or a small ant), but if
there is any good (done), He doubles it, and gives from Him a great reward”

[an-Nisa’ 4:40]

“So whosoever
does good equal to the weight of an atom (or a small ant), shall see it.

And whosoever does evil equal to the weight of an atom (or a
small ant), shall see it”

[az-Zalzalah 99:7-8]. 

Our advice to the questioner is to notice what is mentioned
in his question of extremism and going out of one’s way to make connections
where there are none, which is blameworthy. 

The first example is connecting the validity of the fast to
praying in congregation. The ruling on that has been outlined above. 

The second example is asking about forcing his mother to pray
in congregation with her son. The Muslim should be well aware of the great
rights that parents have before Allah, may He be exalted, and what the son
is required to do of lowering the wing of humility to them, treating them
kindly, speaking nicely to them, and being polite in his dealings with them.
So how can these qualities be combined with forcing and compelling? Can
anyone be forced to do any act of worship? Or can any act of worship be
valid if one is compelled to do it? So how about if that compulsion is
directed towards one’s mother, who is entitled to the greatest share of
respect, honour and kindness?!

All of this leads us to advise you to think again about the
reason why you have stopped praying in congregation in the mosque. Perhaps
there is some flexibility in the matter of which you are not aware. Perhaps
the Shaytaan has motivated you to go to extremes in forsaking the
congregation because of what he has made you imagine of clear mistakes that
render the imam’s Faatihah and prayer invalid. This is not a far-fetched
notion, because the Shaytaan lies in wait for man and uses every means at
his disposal to bar him from the path of Allah and encourage him to make
things too difficult for himself in both religious and worldly affairs. So
beware of falling prey easily to his whispers, and protect yourself by
seeking knowledge and adopting a moderate approach. 

Whatever the case, whoever takes measures to join the
congregation, and is keen and strives to do so, and does not let anything
deter him from that except a legitimate shar‘i excuse on which there is
scholarly consensus, such as sickness and the like, we hope that Allah, may
He be glorified and exalted, will decree for him in full the reward of
praying in congregation, as an honour from Him, may He be glorified, as our
Prophet (blessings and peace of Allah be upon him) told us when he said: “If
a person falls sick or travels, there will be recorded for him a reward like
that of what he used to do when he was at home and was in good health.”
Narrated by al-Bukhaari (2996). 

Al-‘Allaamah as-Sa‘di (may Allah have mercy on him) said: 

Deeds vary and the size of the reward depends on the extent
of faith and sincerity in the doer’s heart, to the extent that the one who
has a sincere intention – especially if it is followed by whatever he is
able to do of good deeds – he will be like the one who does that deed.
Allah, may He be exalted, says (interpretation of the meaning):

“He who
emigrates (from his home) in the Cause of Allah, will find on earth many
dwelling places and plenty to live by. And whosoever leaves his home as an
emigrant unto Allah and His Messenger, and death overtakes him, his reward
is then surely incumbent upon Allah”

[an-Nisa’ 4:100].                                                           

And in as-Saheeh it is narrated in a marfoo‘ report:
“If a person falls sick or travels, there will be recorded for him the
reward of what he used to do when he was in good health and was at home.”
“In Madinah there are people who you never travelled any distance or crossed
any valley, but they were with you – that is, in their intentions, in their
hearts and in their reward – but excuses prevented them from joining you.”
If a person thinks of doing some good deed, then he is not able to do it,
his eagerness and intention to do it will be recorded for him as one
complete good deed. 

End quote from Bahjat Quloob al-Abraar wa Qurrat ‘Uyoon
al-Akhyaar (p. 16) 

For more information, please see the answer to question no.
194317

And Allah knows best.