Sorry, I can’t help you with your problem. I suggest you create an issue report at Brave GitHub and/or Chromium Bugs. Brave community members and support staff can probably provide basic troubleshooting information, however, if you have already tried the things suggested, you are more likely to get a technical response if you create an issue report at Brave GitHub and/or Chromium Bugs.
Probably what you call training wheels information below, but posting anyway. 
Blocked Ports:
I couldn’t find Brave specific documentation, but found info at The Chromium Project (which definitely apply) and chrome (which may or may not apply). Also posted some Brave GitHub issue reports per proxy setups in case it relates, although I couldn’t determine if this information was still valid.
Chromium List of Blocked Ports
https://src.chromium.org/viewvc/chrome/trunk/src/net/base/net_util.cc?view=markup#l68
// The general list of blocked ports. Will be blocked unless a specific
// protocol overrides it. (Ex: ftp can use ports 20 and 21)
1, // tcpmux
7, // echo
9, // discard
11, // systat
13, // daytime
15, // netstat
17, // qotd
19, // chargen
20, // ftp data
21, // ftp access
22, // ssh
23, // telnet
25, // smtp
37, // time
42, // name
43, // nicname
53, // domain
77, // priv-rjs
79, // finger
87, // ttylink
95, // supdup
101, // hostriame
102, // iso-tsap
103, // gppitnp
104, // acr-nema
109, // pop2
110, // pop3
111, // sunrpc
113, // auth
115, // sftp
117, // uucp-path
119, // nntp
123, // NTP
135, // loc-srv /epmap
139, // netbios
143, // imap2
179, // BGP
389, // ldap
465, // smtp+ssl
512, // print / exec
513, // login
514, // shell
515, // printer
526, // tempo
530, // courier
531, // chat
532, // netnews
540, // uucp
556, // remotefs
563, // nntp+ssl
587, // stmp?
601, // ??
636, // ldap+ssl
993, // ldap+ssl
995, // pop3+ssl
2049, // nfs
3659, // apple-sasl / PasswordServer
4045, // lockd
6000, // X11
6665, // Alternate IRC [Apple addition]
6666, // Alternate IRC [Apple addition]
6667, // Standard IRC [Apple addition]
6668, // Alternate IRC [Apple addition]
6669, // Alternate IRC [Apple addition]
0xFFFF, // Used to block all invalid port numbers (see
// third_party/WebKit/Source/platform/weborigin/KURL.cpp,
// KURL::port())
Chrome List of Additional Blocked Ports
https://chromeenterprise.google/policies/#ExplicitlyAllowedNetworkPorts
- 554 = port 554 (can be unblocked until 2021/10/15)
- 10080 = port 10080 (can be unblocked until 2022/04/01)
- 6566 = port 6566 (can be unblocked until 2021/10/15)
- 989 = port 989 (can be unblocked until 2022/02/01)
- 990 = port 990 (can be unblocked until 2022/02/01)
Brave GitHub Issue Reports Proxy Setups
Manual proxy setup via Proxy settings doesn’t work in Windows OS’s #20379
Use a local socket for tor socks proxy and control channel where available #650
Other documentation:
Chromium Project Documentation for Administrators/Policy Templates
Basic Troubleshooting:
brave://settings
brave://about
brave://flags
brave://components
brave://net-internals/#events
Update broke DNS? - #4 by fanboynz
Is problem reproducible in new test profile, Beta, and/or Nightly?
Other Stuff:
Deviations from Chromium (features we disable or remove)