Several questions re. performance with bluehost shared server

I'm sorry if this is too long, I'm hoping some of the knowledgeable people on here can give us some advice.

We are developing a multisite wordpress installation and we realise that shared hosting with bluehost is not ideal but we're hoping that it will be OK while we still have a small number of users. So far we are just testing with about 10 sites and very few products.

It seems a bit slow to us, but we're not sure what to expect. One of our testers gave this feedback "OK, so I went on to the site and the speed is a bit weird... it started out very fast - loading quickly but as i went further into each shop and back to main page, then to another shop then back to main page etc etc it got slower and slower (with each click) - not sure that is helpful? It is almost like something is tying it up in some way?"

1) Are we trying to be too ambitious by using all of these plugins: marketpress (SimpleMarket theme with a child theme), buddypress, bbpress and Another Wordpress Classifieds Plugin?

2) Is bluehost shared hosting just a bit slow so we have to live with it if we can't pay more?

3) The wpmu org blog suggested using the Hyper Cache Extended plugin for shared hosting but said it hadn't been tested for mulitsites. Has anyone used it successfully on a multisite installation?

4) Our bluehost cpanel says we are running PHP 5.2 and I'm nervous about clicking the option to switch to PHP 5.4 because it says at the top "If you are not familiar with these options, do NOT change them.
This can cause all PHP scripts on your site to stop functioning if misconfigured". Is it worth the risk?

5) I ran the P3 plugin profiler and got the following results but have no idea whether these are as good as can be expected given what we are trying to do, or whether they suggest we have a problem.

WordPress Plugin Profile Report
===========================================
Report date: September 9, 2013
Theme name: SimpleMarket
Pages browsed: 10
Avg. load time: 2.4714 sec
Number of plugins: 35
Plugin impact: 79.07% of load time
Avg. plugin time: 1.9542 sec
Avg. core time: 0.3846 sec
Avg. theme time: 0.0342 sec
Avg. mem usage: 120.03 MB
Avg. ticks: 40,737
Avg. db queries : 136.60
Margin of error : 0.0983 sec

Plugin list:
===========================================
P3 (Plugin Performance Profiler) - 0.0075 sec - 0.39%
WPMU Assist - 0.0026 sec - 0.13%
Admin Menu Editor - 0.0797 sec - 4.08%
Author Avatars List - 0.0271 sec - 1.39%
Badgeos Community Add On - 0.0052 sec - 0.27%
BadgeOS - 0.0860 sec - 4.40%
Blogs Directory - 0.0028 sec - 0.14%
New Shop Templates - 0.0245 sec - 1.25%
Buddypress - 0.3131 sec - 16.02%
Contact Form - 0.0017 sec - 0.09%
Custom Content Dashboard Widget - 0.0016 sec - 0.08%
Dashboard Widgets Order - 0.0021 sec - 0.11%
ET Shortcodes - 0.0931 sec - 4.77%
Global Site Search - 0.0009 sec - 0.04%
JHB default text - 0.0002 sec - 0.01%
jhb remove admin bar item - 0.0478 sec - 2.45%
MarketPress - 0.1329 sec - 6.80%
Members Directory - 0.0059 sec - 0.30%
MP Product Search Widget - 0.0042 sec - 0.21%
Multisite User Management - 0.0077 sec - 0.40%
Shortcode Widget - 0.0011 sec - 0.06%
Set Blog Description on Blog Creation - 0.0010 sec - 0.05%
Set Password on WordPress Multisite Shop Creation - 0.0013 sec - 0.07%
Signup TOS - 0.0094 sec - 0.48%
Site Categories - 0.0425 sec - 2.17%
Snapshot - 0.0439 sec - 2.25%
Ultimate Branding - 0.1980 sec - 10.13%
WP Customer Reviews - 0.0113 sec - 0.58%
Wp Google Fonts - 0.0164 sec - 0.84%
Wpmudev Updates - 0.0244 sec - 1.25%
Another Wordpress Classifieds Plugin - 0.4127 sec - 21.12%
bbPress - 0.2745 sec - 14.05%
Formidable - 0.0512 sec - 2.62%
GD bbPress Attachments - 0.0075 sec - 0.38%
Password Protected - 0.0124 sec - 0.64%